If you wanted to paint these stepping stones I would use Patio Paint. It is made for outside painting. You can buy this paint in small bottles at most craft stores. You can also combine colours and put it on with a small sponge to give you a mottled and more realistic effect. Also you can buy a paint book to see patterns of different stones to create a faux finish. Happy painting!

I saw alot of different ways to paint or stain concrete in the garden junk, hypertufa forums. You might also do a search which will bring up different idea from various forums. They do have concrete stains now. Good luck