Hmmm... I don't know much about Marvel, so I will have to rely on basic stereotypes of their characters:
White: the Beyonder (yea.. I said it... I'm thinking of the guy who the Illuminati met recently)
Black: Thanos (Death's lover and all that)
Red: Bruce Banner as the Green Hulk (a colorist's nightmare)
Orange: Dr. Doom (that guy craves power...)
Yellow: Green Goblin (cuz he would revel it...)
Green: Spider-man (but not Peter Parker, cuz that guy is a wuss)
Blue: Professor X (never, ever gave up...)
Indigo: Aunt May (after all, she lets that shulb stay with her)
Violet: Steve Rodgers as Cap. America (love of country... but really I just wanna see him in a Star Sapphire outfit with the star...... in that..... in that..... you know..

)