Laser sensitive coating / paint

here's a patent :
Patent US4844947 - Technique for the application and cure of photosensitive paints - Google Patents

Btw. try this forum:

Lasers

It has more pros .. just don't say you come from here, cause they don't like us balloon poppers. :shhh:

I remember a little solar paper kit I had as a kid, it came with these square pieces of what felt like origami paper. The paper was in a black plastic protective pack, and was blue in color. When you put it outside, you'd put leaves on top of it, and weigh it down with a clear piece of plexiglass and set it out int he sun. Now, I don't remember how, but I do remember somehow that resulted in a blue outline with white shapes. It's been so long, I was probably toddler aged or something.

I think that would be your best bet, though, is finding out what dye they used and incorporating it into the sand/cement mixture that you use, and then lasering it so that it changes color and you have a "stencil" printed onto the work to work with.

If you only need it to temporarily show the pattern, you might consider checking the link in my signature. There are a few options there which can respond to 405nm lasers and is easily visible in daylight, just not for very long.