Yes cocoa would be fine, I do not object to that. Blue mugs make tea look weak though, which in turn makes it taste weak, and there's nothing worse than a weak cup of tea.
I collect one mug from each skiing resort I visit. It's really the only thing I make a point of doing collecting-wise now. Most of them are stuck together with glue and therefore undrinkable from now though, as I insist on actually using them, which is probably contraindicated for a mug collection.