Pentel Acrylic Gouache is an opaque paint made with acrylic resin. You thin it with water. It works on paper, and also on wood, plastic, stone, paper clay, and other surfaces that are free of oil. The paint comes in laminate tubes that are easy to squeeze.
There are two sets: 8 colors (9 tubes, with 2 whites) and 12 colors (13 tubes, with 2 whites). The 12 colors are also sold as single tubes.
Because the paint is opaque, a new layer covers the color underneath. Once dry, it is hard to wash off.