Yes, concrete does vary in color to a degree. I'd suggest looking at something in your area, photograph it if you can. Mix a small batch keeping track of the ratio of colors. Put some on a sample piece of what you will be painting and let it dry. Once it's dry compare it to your photo or take it with you and compare it with the real thing. Remember to let the paint dry, as it may change color as it does.
Good luck,
Richard
