See "Stepping Stone Recipe" post, the next one down. The recipe that was given to me stated that you could add latex paint to the concrete mix. The lady who gave me the recipe said it was a good way to get rid of leftover paint.

to be latex? or would any paint do?

I would use up any paint that cleans up with soap and water (acrylic latex, latex). I would not use oil-based paint in a stepping stone mix.