Author Note: Just a random drabble I thought of in the middle of the night, so I'm sorry about any typos there may be (pointing them out to me would be most helpful). I do know that the colours that follow aren't quite the spectrum, but I needed to write down some of specific ideas in my head, and there wasn't quite colours for them, so I used some artistic license. :-).
This contains a lot of pairings that are quite varied, and my only excuse for that is that I tried experimenting. Sorry in advance :-)
Pairings: Chekov/Sulu, Spock/Kirk, Bones/Uhura, Spock/Uhura, Sarek/Amanda
Red is the colour of human blood and yet it is strangely absent when Amanda Greyson dies. Death is so much more sudden then Spock had imagined it, and he always expected it to be something obvious and loud, a gesture from the universe that something important, something that should have been was missing. He was wrong however. His mother's death is quick and unassuming and everything is so quiet afterwards, as though nobody but he has noticed she is gone. There is no body to bury, no Vulcan to bury her body upon, no time to say goodbyes, and the only thing Amanda Greyson leaves behind is a lifetime of memories, and an empty bloodless transporter pad where she stood have stood.
Pink is the colour of the rose McCoy leaves outside Uhura's quarters one day. It's a lapse of weakness on his part, being a southern gentleman of honest intentions; he should have waited longer, waited for some sign. She's only just broken up with Spock, he thinks angrily to himself, although the break had been coming for a while and both parties were still firm friends. She's not going to want a serious relationship with an older grumpy physician, who's already been and married once. His heart tells him differently however when he sees her pick up the flower, holding it in her hands, fingering the blush-hued petals and muttering McCoy's name, his real name, in the way only she can. Perhaps there is hope yet.
Yellow is the colour of Hikaru Sulu's uniform top and it's a colour that Pavel Chekov sees every day. He likes the golden hue of his partners' shirt, although he definitely prefers it when Sulu isn't wearing it and Chekov gets the view of the helmsman's lithe muscled torso. However, every morning, Chekov is always the one awake to see Sulu off on his shift, passing the yellow shirt over with a tired smile, just glad that he gets to spend his mornings with his helms partner, because he can think of no better way to spend his day.
Green is the colour of Spock's cheeks when he blushes- a sight that, although rare, is not unseen. That green is something that Jim Kirk is always striving to see more of, even just a pale hint. It always makes his heart feel a little bit lighter when he sees his First Officer blush and turn away at a suggestive comment by Jim directed at the Vulcan, or when Kirk's body proximity in the turbo lift just gets a little bit too close be completely innocent. Kirk can't blame himself for trying, the guy's single now so it's allowed, especially with Uhura turning a blind eye for Spock's sake. Every time Kirk gets a reaction, that vague tint of green, it gives him more hope for the future, although he wishes that the Vulcan would just hurry up and get the hint.
Blue is the colour of Pavel Chekov's eyes. It's a particular shade of blue, the colour of cornflowers, and a colour that Sulu sees every day, every morning when he wakes up and every night when he settles down to sleep. It's the same hue throughout everything, every feeling, every emotion, and every circumstance. An affection glance when the Russian thinks no one can see, expressions of fear or anger or passion. It's always the same blue that holds Sulu steady throughout everything, and one look with those cornflower eyes is enough to make him fall in love all over again.
Mocha is the colour of Nyota Uhura's skin as her slender deep brown fingers rubs against the pale white of Spocks. It's times like this, when the two of them are finally alone, that Spock feels most at home aboard the Enterprise, his nature not at war and his thoughts not so conflicted. During these tiny snatches of rest bite, he feels just like he has to be himself for Uhura, no one else, as he loses himself and his logical control in the softness of her Mocha skin and her burning touch that cleanses him in a all-consuming fire of emotion.
Indigo is the colour of the scarf that Sarek buys Amanda. It's not as though it's her birthday or nearing the Earth holiday of Christmas, and he finds himself buying it simply because he wants to, because he loves her. He purchases it while he's on a diplomatic mission, fulfilling ambassadorial duties on the planet of Daskan Prime, seeing it on sale by pure chance in a market place near to where he is staying. Such vibrant colours aren't found on Vulcan that often, neutral colours such as beige and tan dominating despite bright, deep colours complimenting his wife beautifully. He finds himself buying the cloth for her anyway, logic be damned, thinking of how the richness of its hue would perfectly match the colour of her eyes and imagining the expressive smile on her face as he tries to keep a loving one off his own.