Now I am not sure, if I am 100% correct on this but colored enemies, are a rarity kinda thing. You can compare it a little bit, with Items in RPGs. Grey are weaker than normal enemies. Green are stronger. Red are I believe the most powerful enemies. Pink tend to prio Sexual Attacks, like remove clothing, jerking off etc. Now what exactly every color is, dunno. For Passives, there it is just, what kind of Category there are in. Sadist Stuff is turquoise. Exhibition is bright green etc. But again, not 100% sure on that one.