To color the concrete for the driveway on the Kuppersmith Project house, powdered colorant was poured into a paper grocery sack and dropped into the concrete truck. The colorant was thoroughly mixed into each load of cement before it was poured. Since the powdered colorant made the concrete stiffer, additional water had to be added to the mix.
Another option for coloring concrete is to apply a color hardener to the top layer of concrete after it has been poured. While a color hardener can produce more vibrant colors than adding colorant to the mix, any dings or edges in the finished slab will show, since the color is only on the surface of the concrete.
Watch this video to find out more.