Earth Color Kit
The Stone Gray seems a bit dark when applied directly to create rock from foam putty. So, I shake the bottle to mix the pigment up as usual. Then I add enough water to fill the cap about one-third to one-half full with a dropper. The cap already has a lot of pigment in it from the shaking, so I just mix it in with the water. If I need more, I put the cap back on, shake, and then add water again.
Burnt Umber and Yellow Ochre, the only other colors that I use to create rock, can be diluted similarly, although they probably need less dilution.