I forgot to add that I did experiment with paint. I had tubes and bottles of acrylic paint left over from other projects. I added paint to the water before adding it to the dry mixture. I used all colors to get different shades for each rock. Also, I used the plastic bag trick...2 shopping bags gave nice wrinkles. Placed each in it's bag along the edge of the walk, and removed the bag in a couple of days. If I used the paint in a container or pot, it would hold water...good for a bird bath but not if I wanted the pot to drain naturally.
Thanks for all the info learned on this site ;) Sharon