Thea did this one with me we were experimenting with painting with textures rather than brushes. I think we used cardboard, plastic, sponges, screws and maybe other things. It turned out pretty fun. She made her own which she almost turned into mud mixing all the colors together.
The second I did on my while my kids were playing actually. I just picked three colors and painted it. I have been really into neon colors and had this neon yellow from my failed neon yellow chair project.