Oils from your kitchen, from food, or even from your hands will get in the way of the paint sticking to the ceramic’s surface. It is not ideal if you want your efforts to last!
Right underneath the purple, paint a green semicircle. I think it looks nicest when there aren’t any gaps between colors, but this is entirely up to you.
Acrylic paint takes anywhere from 20 minutes to 2 hours to be touched dry, depending on its thickness, but you’ll need to leave it for 1-4 days to dry completely solid before it is safe to hand wash.