Painting on Stones Is a Craft That Rocks! FeltMagnet
Paints All kinds of craft, water based, or acrylic paints work well for rocks. One downside of acrylics is that they tend to be difficult to wash out of clothes, so be careful when using them. Wear a smock and put down something to protect the painting surface. If you're painting with very young children, tempera paint is the way to go because it washes out much easier though the colors aren't as bright. If your rocks will be living outside, make sure to use patio paint or outdoor friendly paint.
Test out your paint on paper before painting your rock to make sure you don't have any surprises with consistency or color.