I had been using watercolors, but have noticed that it rubs off a bit, so I tried these:
Crayons that work like watercolors, the colors are bright and don't come off!
I first carefully color white tissue paper, I tend to use more than one color to get the right shade.
After you go over the color with a brush dipped in water, it looks like this.
Once it's dry you can start using it.