Yes, a little pink here or there can be cute (as I've demonstrated before), but I don't think it is a prerequisite.
Case in point: The green puppy dog onesie that I picked up before I knew our baby was a "she."
Paired with some (girly) polka-dot leggings and you've got yourself a cute little outfit.
Onesie: Carter's (thrifted for $0.25)
Leggings: Carter's (thrifted for $0.50)
No pink necessary.