If you draw on it long enough, keep adding to it, it eventually becomes gray.
This is the third version. Partway through the first version I decided to add the beams of light. Too late, too sketch-like. Partway through the second version I decided… well, there were things I liked about each of those, and my evaluator, Trish, liked the first one best. But, partially because I’m working on putting together a ‘real surfers’ coloring book, I went with something, probably a bit more, um, draftsman-like. Nah; can’t quite master that. I have this, and, when I tried to make a copy, this weird tire-tread-like line went down the right side, so, not risking the original, I may not actually color this. Yet.
Really on the coloring book. I’m just trying to figure out how I can do it at a reasonable price, and, of course, how the hell I’ll try to market it.