....without it bleeding? How far in advance can I do this? Any help appreciated!!!

Anyone?? Please??

Do you mean navy buttercream on ivory- it shouldnt bleed if it doesnt sweat

If you don't need to put the cake in the fridge you should be fine. It's the sweating that causes problems. If you do have to refrigerate the cake, I would either not do the navy on the ivory, or I'd do it right before delivery and after the cake has once again come to room temp.

Ok...then I think I'm good to go. No refrigeration needed. Navy bc piped on ivory bc. I've piped darker colors on fondant before but never bc. Thanks so much for the responses!