While painting the dull gray surface of standard concrete works, I knew there had to be a cooler way of coloring these little plant homes. After some research and hands-on testing, it turns out that the trick is starting with white concrete and stirring in powdered pigments. From there, the sky's the limit. Marble them, create an ombre stack, go two-tone. You really can't go wrong with this foolproof project, and they're ridiculously fun to make.