Ichijo Takuma, was white fire, so pure and blinding in that purity, but the very thing that burned so bright and hot was the very thing that would bring him to his end, buring himself out 'till there was nothing left but cold ashes.
Ruka was orange fire, beautiful and attention catching, but for all that it was dreadfully ordinary. He and Hanabusa also fit in with her. Each fit a stereotype, they were what they looked like.
Shiki and Rima were yellow coloered fire. Just burning on the edge of things highlighting the orange but never becoming part of it.
Kaname was black fire, enchanting and deadly, toxic and choking. Powerful and frightening.
Yuuki was torn, her color flickering back and forth orange, white and black. His heart hurt, when he saw the black steadily overpowering the other colors.
Kiriyu Zero was red fire, the very heart of fire. The hunter looked cold, his very coloring put one in mind of ice but everything else about him, his personality, even his fighting, was filled with burning passion. Everything from his hatred of Kaname and vampires to his aching love of Yuuki. It was all filled with the same red hot passion. Zero, Kain thought, would be the one left standing in the end, for he'd survive, even if all that was left were a few coals, all it would take was a bit of air and some fuel and he would return.