Shower Paint Pallet

My wife made shower paint for my children made from corn starch and requested that I made her a pallet to keep them in. She didn't want to traditional pallet because it wouldn't be easy to set down in the tub. So I made her one that resembles trays she has at school (she's an art teacher) that is rectangular enough to put on the tub ledge.

This is v1, I told her I will also work on a version that I can put suction cups on the back and put it right on the shower wall.