This is a companion piece to 'Walk With Me', a Castle tribute to Stana Katic's ATP movement. 'Start Wearing Purple' by Gogol Bordello is a song from Stana's ATP playlist. This is the first in the 'Colors' series of one-shots.

A/N: This spin-off is dedicated to the lovely BlueOrchid96 who asked so nicely, (translation: begged) for the tiny scene mentioned in 'Walk With Me', where Castle recalls singing a duet with Kate at a New Years party, his purple silk tie wrapped around her neck. So, as usual, one thing led to another, and this was the result.

Start Wearing Purple

"With you in that dress my thoughts I confess

Verge on dirty…"

'Come On Eileen – Dexys Midnight Runners

"You in that dress," sings Castle, sidling up behind Kate, covertly caressing her silk covered ass as he skates past with a tray of drinks, the low, rumbling tone of his voice tugging at something primal inside of her, making her vibrate even when he's halfway across the loft.

It's New Year's Eve and they're throwing their first joint party to celebrate this year.

Kate moved into the loft on 28th November – Thanksgiving night. They had had dinner as a family, Kate's dad even joined them this year, and the day was a great success – easy, fun, family time. Then, as they stood side-by-side at the sink with the night drawing to a close, rinsing dishes and washing glasses together, a quiet sadness settled over both of them, until Castle turned to Kate and uttered just one word.

"Stay."

The forever part was plainly implied by the deep longing in his eyes and the heartbreaking way that one short word caught in his throat; his voice breaking over it like a wave on the shoreline. Writer, rendered nearly speechless by an aching hope for a simple yes.

She didn't keep him waiting long.

"Sure this is what you want? Because if we do this, Castle…"

"No take-backs, Kate. I promise. Just…don't go."

"Ever?" she grinned, sliding her damp hands around his waist and stepping into the cradle of his hips.

"Ever," he agreed, nodding slightly, resting his forehead against hers, sharing airspace, a kitchen towel thrown casually over his shoulder, the sound of their family chattering in the background.

It wasn't spectacular or showy or even particularly private. But it was intimate, and sizzling, and just so perfectly them.

"I have nothing with me. No clothes, no shoes, none of my…favorite books…" she teased, rubbing her nose gently against his.

"I'll buy you new clothes and shoes. Whatever you want, Kate. I'll even write you another book. Heck, I'll write you a whole series. Oh, that's right, I already did that," he grinned, feeling her smile as she gently kissed inside his collar where his skin was so soft and warm and tender, just like his heart.

"Just tell me you'll stay?" he whispered, his voice catching again. "I don't want us to be apart…not…I need you, Kate. I love you."

And this was the first time he had uttered these words since he'd yelled them at her in her apartment months ago in an effort to save her life.

Well, he had done that alright. But more than that, he had transformed her life into something more wonderful than she could ever have imagined for herself. She got to share so much with him now – her sorrows and frustrations, her joy and happiness, her successes and failures, her weepy days and weak moments, her needs and desires - everything. She shared all of them and he shared right back. Gone was the cocky, sure-of-himself, bestselling author-slash-playboy. Hello vulnerable, insecure, tenderhearted, playful, funny, kind, thoughtful, patient (and who'd have put money on that?), sexy, sensual, immature (yes, still that), loving, loyal, hardworking, tenacious trier that was the real Richard Castle. And she was in love with him too.

"Throw in some closet space and you have a deal," she whispered in his ear, up on her tiptoes, hands resting on his shoulders for balance.

"Really?" he beamed, pulling back to look at her.

"Really," she nodded, eyes glittering with careful determination and something he hoped was excitement and maybe even joy.

"You can have all the closet space you need. Hell, you can remodel the whole damn loft if you want…just…Kate, you really mean yes?"

"I really mean yes, Castle," she whispered, kissing him softly, fingers sliding through his hair, as a deep need for this man surged through her.

She was vaguely aware that the low hum of conversation coming from Alexis, Martha and her dad had abated to the point of silence, but she couldn't bring herself to break up this momentous moment between them to check.

As was proving to be the case so often these days, Martha did it for them.

"Kiddos, is there something we should know? Because I don't see much dish washing going on over there," she had pointed out, loudly.

Castle had groaned, buried his face in Kate's neck while she cupped the back of his head tenderly, shielding him for a second.

"No hiding from her now," she whispered, lightly scratching his scalp, feeling him shiver against her. "She's part of this package deal too."

"You. Are. Amazing," he had told her, taking both of her hands in his and kissing her knuckles.

"You're not so bad yourself, Mr. Castle. Now…should we tell them?"

So, Kate moved in Thanksgiving night with nothing more than the clothes she stood up in. The movers came the following week and shipped the bulk of her stuff to his place, sending a few extra pieces of her art and furniture to his Hamptons house to be rearranged later, whenever they got a chance to get a weekend away.

They've been ATPing to work by subway at least once a week, when cases allow, and since Kate had to change her address on file with the Department and come clean to a surprisingly accommodating Captain Gates, she even holds his hand in public these days – both above and below ground.

But now we're back here, hosting their first New Year's party together at their loft, and it is seriously in full swing.

The ball already dropped in Times Square, ushering in the opening minutes of 2014, and the music is loud, thumping - the thudding kind of beat that resonates in the center of your chest and makes you dizzy. The occasional squeal and burst of raucous laughter floats above the heavy bassline, reflecting the high spirits of the crowd. Castle's neighbors have all been invited to the party too, short-cutting any awkward noise complaints.

"Lanie!" calls Esposito, waving his on-off girlfriend over. "You and Beckett are up next. Pick a song," he tells her, thrusting a playlist into her hands and grabbing another beer.

"Like you even have to ask," she drawls, pushing the book back onto Javi's chest.

"Not…"

"Ya' huh. Y'all better prepare yourselves. Cause the girls are in the house," she squeals, performing a devastating wiggle that sends Esposito's blood pressure rocketing.

"Hey, Castle. Got any Tequila, man?" yells Esposito, signaling to the host.

"That bad? What's up? You and Lanie fighting again?" asks Castle, looking around the room for the M.E.

"Nah. Lanie & Beckett are up next. You ever seen those two sing together?" he asks the writer.

"Uh…no. Nope. Should I be…worried?" he asks the detective, watching the two women sashaying over to the makeshift stage area, Lanie staggering slightly as she leans on her taller friend, giggling helplessly.

Kate taps the microphone and it whistles piercingly.

"Sorry," she breathes into it, her eyes instantly locking onto Castle's when she stands up straighter, the improvement to her posture automatically thrusting her breasts higher.

She's wearing a purple silk wrap dress and has this amazing violet lace and satin lingerie set on underneath. It took her three attempts to wrap and tie the dress around her tonight, after Castle came out of the bathroom, still shower damp and wearing only a towel, to find her dressing. He attempted to intervene and divest her of said dress so that he could get a better look at her lingerie.

"For later," she had insisted, closing the cool, silky folds of the garment around her, and then getting him to help her tie the belt at the back.

"You know I'll only be staring at you all night, imagining what little I've just seen," he had told her, sliding his hands around to rest on her stomach, marveling at the way the fabric draped and clung to her subtle curves.

"If you get a damp spot on the back of my dress, Richard, so help me," she had warned, elbowing him off with a helpless giggle when he slapped her ass.

So now he is standing in the middle of their crowd of friends, helplessly staring at his beautiful girlfriend as she prepares to strut her not inconsiderable stuff on stage. And he's trying to tear his eyes away from the delicate outline of her nipples that he can clearly make out through the fine layer of lace-covered-silk, just hoping no one else can, when she gives him that look; not the scolding one, the totally hot one that says 'I know what you're thinking right now and I want that too', and his knees go weak.

The girls start to sing the Dixie Chicks' version of 'Goodbye Earl' and everyone is laughing and pitching in when they know the words. But Castle only has eyes for Kate, and, from the way she's staring over at him, she is stuck on him too.

'The cops came by to bring Earl in

They searched the house high and low

Then they tipped their hats

and said "Thank You ladies,

if you hear from him let us know"'

When Kate pretends to tip an imaginary hat, she leans forward slightly, and Castle gets a dazzlingly glimpse of violet lace when the long, white gold pendant she's wearing swings between her breasts and catches the light.

He wants her off that stage and into their bed now.

Lanie links arms with her and she sways through the rest of the song, girl power incorporated as the M.E. yells in Javi's direction:

"'Cause Earl had to die!"

"Told you, Castle. Those two up on stage with a mic…things start gettin' ugly pretty damn quick."

"I…uh…we need to get them down from there. Lanie looks ready for an encore and I need to…Kate is…" he babbles, his mouth dry and hands sweating, until Esposito finishes downing his shot and takes a look at his friend.

Castle is staring at Kate with such naked longing that the remainder of the alcohol catches in the back of Esposito's throat and he coughs hard.

"Do not say anymore, bro. What happens between you and Beckett is totally not something I want to be thinking about. I'll take care of Lanie. You deal with your own chica. And what is with the matching clothes tonight, anyway?" asks Espo, flipping Castle's purple silk tie.

"Kate chose it. She…yeah, she totally surprised me too," he grins, remembering how she'd taken the red necktie he was planning to wear with his white shirt and black suit out of his hands, and replaced it with this purple one that totally matches her dress.

Esposito shakes his head slowly, and then pats Castle's chest.

"You guys are great together, you know that. But there are times you really make me want to vomit, dude," he adds, punching Castle playfully in the shoulder. "This is one of them."

Lanie and Kate come down off the stage after an interminable minute of bowing and soaking up attention the way only drunk women can.

"Your turn, stud," slurs Lanie, poking Castle in the chest.

"Ow!" he yelps, backing away from the M.E.'s vicious poking finger and bumping into Kate's front.

And how the heck did she Ninja her way behind him?

"Trying to escape, Castle?" she drawls, the fingers of her left hand flirting with his left butt cheek.

"No. No!" he exclaims, spinning around and catching her wrist before she can light him on fire anymore.

"Then we're up."

"We're…? We're what?" he gapes, as she drags him away from their friends and back towards the stage.

"Kate," he whines, tugging on her hand, his free hand settling on her sexy, slender waist. "I need you," he hisses in her ear, letting his arm slip all the way around her middle so that she's pressed back against his chest.

He catches Captain Gates' eye and drops his hand immediately, thinking 'even in my own home that woman has me whipped'.

"Soon," she promises, curling back to kiss his jaw. "First, we're singing…just like we practiced," she tells him, towing him towards the front of the room by his own belt.

"Practiced? What are you talking about?"

He's worried she's about to give him hell for not paying attention again, but he has simply no recollection of practicing anything with her that might be considered remotely appropriate for a performance in public on stage in front of their friends and family.

Whatever it is she's about to say, he's also fairly certain he isn't drunk enough to go through with it.

"Our playlist. Come on, you know," she teases, her red lips parting as she peaks out her pale pink tongue between a row of perfect white teeth.

"Re…uh…Kate, you're gonna have to remind me, and please can you stop with the tongue right now. It's…it's delicious babe, but seriously distracting."

"Okay, babe," she sings, touching his chin with one seductive finger. "Look at our clothes. Giving you a clue?" she asks, swaying against him so he has to catch her by the hips to steady her, and he's not sure if she really is that drunk or if she's just toying with him.

But hell, it's cute as, so whatever.

"Nightclub bathroom, we were singing…among…other things," she adds, as an additional prompt, since he still hasn't the faintest idea.

He looks down at her dress and almost wishes he hadn't. Her cleavage is glistening with this fragrant body oil she put on earlier, and he can barely tear his eyes away from the soft mounds of her breasts and the drape of purple silk over her hips…

Purple!

"No," he says, rather fearfully. "Not…no!"

"Ya' huh. Gogol Bordello, Rick. Come on," she tells him, grinning enthusiastically, dragging him now up on to the little platform stage with one heck of a force.

And so maybe she is that drunk after all, if she's prepared to totally embarrass them both in front of her coworkers, their friends, his neighbors, his daughter and her very disapproving boss.

Unfortunately, she is not too drunk to operate his iPod it seems, and almost immediately the jagged, Gypsy punk strains of the crazy, way-out, romp of a song, 'Start Wearing Purple' fill the loft.

Heads snap up, people spin in their direction, drinks slosh in glasses like a Carnival cruise liner pitching in a storm, and suddenly there is Kate Beckett, grabbing him by his necktie and parading him like some Roman sex slave across one end of his own living room.

'Start wearing purple wearing purple

Start wearing purple for me now

All your sanity and wits they will all vanish

I promise, it's just a matter of time...'

By the end of the first verse, Kate is grinding up against him, and the crowd is cheering her on through this rousing drinking song, led from the front of course by sassy catcalls from Lanie and one heck of a wolf-whistle from his own crazy mother.

Kate works quickly to relieve him of his necktie - once she's finished using it to lead him around like a dog on a leash that is. Her fingers scorch his skin when she pops the top button on his shirt, and then she slides it slowly and seductively out from under his collar, while singing some guttural, filthy sounding words that he thinks he vaguely remembers are Ukrainian or Slovenian, before wrapping the silk tie around her own bare neck.

'So Vio-Vio-Violetta! Etta!

Va-va-va-vaja dama ti moja!

Eh podayte nam karetu,

vot etu, i mi poedem k ebenjam!'

She sings with complete, unselfconscious abandon, and although he feels out of his depth up here performing this particular number as little more than her backup, or a prop, (despite backup being a familiar role for him), he can't deny her this. She looks spectacular, so powerful shimmying his tie around her neck like a burlesque dancer with a feather boa. Her eyes are shining and haven't left his the entire time. He feels as if he has been caught in a million watt Kate Beckett spotlight, like the proverbial deer in the headlights, and he never wants to leave this particular adoring aura of hers; this warm pool of limelight she's directing his way as if her performance is for him alone.

So he joins in as best he can, playing up every ridiculous pose and performing every raunchy gyration she demands of him, responding to Jenny Ryan's drunken shouts for him to strip by slowly removing his jacket and tossing it into the crowd.

He catches Gates' eye when Kate begins working the little buttons free down the front of his shirt, and finds that the woman is actually smirking at him, no doubt enjoying his discomfort immensely.

Thankfully the song ends well before Kate can strip him naked, but not before her fingers have branded his chest like hot irons, making his body respond to her even in front of this baying mob.

He needs her alone. This party has to wind up really, really soon.

They make their way off stage and into the waiting huddle of their little cop family. Jenny is grinning drunkenly at Castle's partially bared chest, and Ryan reaches forward to close the garment over a little, shielding his wife's eyes until he does so.

"Think we need to get this little lady home," he says, wrapping his arm around Jenny's shoulders. "A little too much excitement for a first night out post-birth," he whispers, though he needn't, since Jenny's sweet, silly smile tells them all she's too zoned out to listen or care.

Nine months without alcohol and eight weeks without sleep have caused the wine she's been drinking to go straight to her head.

"Castle, you and Beckett sure know how to throw a party," Esposito tells him, slapping him warmly on the back. "Happy New Year, man."

Kate catches his eye, and her direct, intelligent gaze tells him all he needs to know – that she is almost certainly completely sober. The whole drunken singing routine was totally for effect, and with that one glance, his night just got one hundred percent better, since there will be no pouring her into bed to sleep this off, and no being gallant or keeping his hands to himself while she snores beside him.

Nope. They are good to go.

The party does break up, but not before Captain Gates corners him in the kitchen while he's busy emptying bottles into his recycling.

"Mr. Castle," she booms, freezing him to the spot, his butt upturned towards her as he stoops over a cardboard box full of empties.

"Uh, Sir?" he stammers, straightening up and spinning round to face her, eyes scanning the few remaining revelers for Kate; for help.

"You throw quite the party," she tells him, eyes narrowed in that way she has of watching him, as if she is anticipating some infraction of her precious rules at any second.

"I…uh…thank you?" he asks, with an uncertain lift to his voice.

"Just wanted to thank you. And may I say, you and Detective Beckett make quite the hot little number up on that stage," she adds, literally freaking him out now with her words and that strange, cutesy grin she busts out on rare occasion.

"That was…really all her doing," he says, only hearing the Captain's praise latterly, when his brain-freeze abates and the words trickle through his Gates-induced stress haze. "Though, clearly she couldn't have done it without me," he adds, deciding that stealing some of the limelight might be okay on this occasion.

"Just…make sure you keep your little stripper routine out of my precinct," she says, ruining some of the effect. "I wouldn't want Ryan and Esposito getting any ideas."

"Yes, Sir," he nods, grateful that his grilling is coming to an end.

"Happy New Year, Mr. Castle," she nods, going to join her saint of a husband in the hall.

When the last guest finally leaves and the loft door closes, he sinks back against it with a long exhale of relief.

He opens his eyes to find Kate right in front of him, sliding his tie back around his neck, her eyes hooded with desire as she leads him gently, wordlessly, towards the bedroom.

He kicks the door closed behind them and the frenzy begins.

"God, I've been dying to get my hands on you all night," he pants breathlessly, running his warm palms up and down over her hips, before he cups her ass and lifts her up, and she squeals in surprise, before he carries her across the room towards their bed.

Kate has her mouth on his neck, and her legs wound around his waist. The skirt of her dress falls behind her in shimmering folds from beneath Castle's hands. When he plants her feet back on the floor, he catches her waist to steady her.

"Sure you're okay to do this?" he checks, looking into her eyes for any sign of dilated pupils, and finding only raw need there instead.

"Oh, fuck, when you look at me like that, Kate," he says, spinning her around until she's facing the bed. "You make me want to do really dirty things to you," he warns.

"It's working then," she laughs, running her hands behind her to grip his buttocks and pull his pelvis up against her ass.

She grinds slowly against him, as if she's doing some erotic dance, and he feels himself getting harder instantly, his erection growing painfully urgent against the firm press of her enticing, curvaceous rear.

"This may not take long," he warns in her ear, cupping her breasts through the warm silk of her dress, before roughly pinching her nipples.

Kate cries out and arches her body, letting her head drop back against his shoulder, exposing her neck to his eager mouth.

"I'm right with you," she groans, circling her hips against his thickening arousal.

Castle pulls her dress aside, exposing one violet, lace-covered breast, her puckered nipple just visible through the opaque screen of delicate fabric.

"When did you buy these?" he asks, rubbing his thumb ever so slowly over the hard, sensitive little peak. "Been holding out on me, Kate?"

"Fuck!" she groans, responding to the way he's teasing her body, but needing more, the ache between her legs so overpowering now. "Weeks ago," she manages to choke out. "After I bought the dress. You...you said you liked the…oh god, Castle…" she cries, when he slides one large palm up the front of her thigh and begins to rub her through the silky fabric, "…the color. I thought…"

But all rational thought has left her, given what he's doing to her sex right now.

"You thought correctly. Looks good on you," he growls, dropping his hand from the front of her dress to slip it around behind, the fabric whispering in a quiet flutter back down over her thighs.

She can hear him unbuckling his belt; the tinkle and rattle of the metal fastening, the slap of leather through the opening and then the pop of a button and the dizzying, provocative buzz of his zipper coming down.

She tenses, excitement flooding her veins, knowing what's coming, her heart pumping harder, faster with delicious anticipation and desperate need.

He frees his erection from his boxer shorts without removing them, briefly stroking along his own length, and then her skirt is being pulled up, the light, slinky fabric thrown up around her waist to expose the backs of her thighs and buttocks. Castle slides his hand around in front of her to cup the dampness of her arousal through her lace panties, and then he swiftly draws them to one side, arching a finger up inside her without any further warning.

"Castle!" she whimpers, grunting a dirty sound of pure need when he adds a second thick digit to the first and curls them inside her.

"Have you been this wet all night?" he growls possessively against her sweat-dampened neck. "With every man out there watching you? Were you waiting for this, Kate?" he demands, sliding his fingers out slowly so that her juices spread over her swollen clit with the long, torturous caress of his skin over hers.

"Yes," she whimpers, clinging to him.

"Bend over," he demands, letting her go so that she can brace her hands on the side of the bed.

As soon as she's down he nudges her legs wider apart and then pulls her panties roughly aside once more. Grasping her hips, he slowly guides the full length of his throbbing cock inside of her.

They both shudder out a long moan of relief at finally being joined together, just as they've both been craving all night.

Castle puts one hand on her shoulder, keeping the other on her hip to hold her steady, and then he starts to fuck her. He moves slowly at first, and Kate helps, bracing herself so that every thrust of his hips is met by tight, gripping resistance from her body, drawing him deeper inside of her on every down stroke, and working him hard on every long withdrawal.

She circles her hips when he stops moving, his full length buried all the way in, driven crazy by the intense pressure, but it's torturing him, and he can feel the need building low in his belly, so he grips her harder and tells her to hold on for the ride before he loses complete control.

Their flesh slaps wetly against one another; the mounds of her buttocks shuddering up against his stomach and what little is exposed through the opening in his pants as they work together, pounding relentlessly towards a climactic high.

He plucks at the bow he tied at the back of her dress and pulls, undoing the wrap-over in one swift move so that it falls apart at the front, exposing her lace-clad breasts and her warm, bare stomach to his greedy hands. The flat of his palm leaves her hip to press against her flexing abdomen, and the extra expanse of naked skin is all it takes to send him flying.

"Kate, fuck, I'm going to come," he warns her, hips bucking even faster now, his cock stroking the mystical ridged surface inside her at such a perfect angle she wants to scream.

She's tingling and aching with this amazing, mounting fire that is burning so bright she wants it to consume all of her; wants him to consume all of her. She feels him throbbing, grinding, seconds before he gasps, clutching her shoulder and her stomach hard, arching his hips up inside her once more before he gives in, spurting into her with a choked cry of release.

He has just enough awareness left to slip his hand inside her underwear as he comes, to lightly brush over her clitoris, his trembling fingers giving her the final help she needs to shatter with him.

The wave of relief that sweeps through her at this new, unexpected sensation, coupled with his loud, powerful orgasm does it for her, and her knees weaken as she follows him over the edge to reach her own devastating climax.

Castle hugs her from behind, his head resting between her shoulder blades while he catches his breath, holding them both upright.

Eventually, he slowly withdraws from inside her, and helps her down onto the bed, tenderly removing her dress and laying it out on a chair, before removing his own clothes to come and lie down beside her.

Her hair is wild against the pillow, her lingerie still more or less in place, and the color compliments her skin tone so perfectly that Castle can hardly tear his eyes away from her - this wondrous, otherworldly vision only he has the privilege to behold.

They curl their bodies around one another, mouths joining for a long, slow, loving kiss; their tongues teasing wetly, stirring up yet another wave of need that will carry them towards the dawn.

"You might want to start wearing purple more often," whispers Kate, feeling her partner smile against her hair, his fingers coasting gently over her ribs, and it's the perfect end to the perfect night, the perfect year, and the perfect beginning to something too.

Purple patch noun: A period of excellent performance, success or good fortune, where nearly everything seems to go right.

A/N: Hope you had fun with that. Amazing what a little ATPing can lead to! Liv.