It's really a personal choice - I mostly think it's about you and what you are wearing rather than about the baby and their gender. My wraps/slings/MTs are a wide variety of colours from brown and blues to olive with flowers, to pinks and reds, but I think that I'd feel comfortable using all of them with a boy.
I would probably ask for pix before making a decision - it might not be to your taste, regardless of colours/patterns.
I would probably ask for pix before making a decision - it might not be to your taste, regardless of colours/patterns.