Well, if you don’t want to walk a whole 3 minutes over to Magenta’s store you can just get stuff delivered. Yellow here is being so rude that he manages to cut off Cyan’s picture balloon halfway off the panel. This is a case where it’s not really evident if they can hear his pictures through walls. Do you need to actually be able to see the balloon floating over his head or do you just see the picture in your head when you “hear” what he says?

Yellow probably just heard him knocking.