All you need is a block of ice (I froze water overnight in an old Chinese takeout container to get a small, rectangular block), water colors, and either a shallow dish or plate to paint on. If you do this outside you can do it right on the sidewalk!
This activity is great for creativity, color mixing exploration, fine motor development, and it's a great opportunity to talk about changing states of matter too (solid to liquid!).
Super simple! Super fun!!!!