Lost: A stone

This curious habit of colouring pebbles and leaving them out in the country, makes you smile. Or does it?

I mean, apart from the colour, it's natural and it reminds you that others have passed this way.

I think I shall paint a few and leave them on my walks. I wonder what the best paint to use would be? Non-toxic , of course. But acrylic or enamel. And should I leave a message?