Harry: Pink, because it brings out your girly playful side.
Niall: Green, because it reminds him of how he is a proud irishmen and that your his four-leaf clover :)
Louis: Red, because of the Red Power Ranger and because he thinks it is the most seductive and romantic color out there prrr :3
Liam: Blue, because of how well it compliments your eyes.
Zayn: Black, because it just suits you soo well. Exspecially black bra & panties, he definetly loves those.