I've seen many mentions of the current enthusiasm for adult coloring books and a friend (thank you, Jean) just sent me a link to the reasons why coloring is good for us. I've known that for decades.
The artists at RubberMoon have been, and still are, creating stamps to delight all of us coloring types. I am sharing some of my designs here as illustrations. The RubberMoon roster is filled with colorable (is this a word? it needs to be) images. Best part, RubberMoon is what we call in the stamping business an Angel Company, meaning anything you make using a RubberMoon stamp and not a copy of any sort you may offer for sale with our blessings. Greeting cards, tags, with vibrantly colored-by-you designs. Hmmmm.
At the company website, images are best viewed by clicking on Shop By Artist link, this is mine. Allow yourself time to browse and choose from among hundreds of varied, versatile stamps. Let every thought narrow down to the point of the pen. You get the idea. (Images are greatly enlarged here. The original sizes leave plenty of room to color.)