Not too long ago I built rammed earth walls for a couple of retired geophysicists. They wanted the walls to look like a stratified outcropping matching the colors of a rock outcrop adjacent to the building site. I made several mock-ups using integral concrete pigments until one was satisfactory. The owners came up with the plan of how thick and what color each layer would be. With that information I calculated the volume of mix for each layer and how much pigment to add based on the mock-up. The ramming process was somewhat encumbered by having several mix piles of different colors and having to switch colors every few inches not to mention keeping everybody on the same page. One of the walls was too long to fill in one day ( I always want to be able to fill whatever form we build in one day to avoid horizontal cold joints.). Coming up with a way to hide vertical cold joints is always an interesting challenge. In this case the same solution was arrived at from both sides. Our crew thought a fault line would match the geologic theme. On the day we were going to propose the fault line idea the owners approached us with the same idea but with all the details worked out. We angled the end-board of the first set. The subsequent set we off-set the layers by a foot or so.
The house was designed by Alan Nicholson. He entered it in some AIA competitions and it actually won. http://hawkesconstruction.com/Nicholson%20story%20board.pdf