All animals have different colors for different reasons that have been adapted throughout time in process as we know called evolution. How these hairs become these different colors in specific patterns is what is up in the air and needs to be discovered. In mice and chipmunk the pinstripe pattern on the back of dark-light-dark pattern. The protein to inhibit facial hair was reconfigured what is known as at least twice through evolution to create the light colored stripes on rodents. The protein is called ALX3.
The pattern is created by three types of hairs. Light, with black at the bottom no pigmentation, Black, straight through, and banded, a mixture throughout pattern. The stripes created by no pigmentation are usually made through mutations but with the chipmunks there is no mutations present so it must be due to a different reason.
What question was needed to be resolved was why was the pigmentation not getting through the hairs. What was discovered by students at Harvard University was that the ALX3 protein was much more active in the white hair than the black or brown hair. This was surprised because the ALX3 protein wasn't known that it was involved in pigmentation. This ALX3 protein interfered with the gene called Mitf and that is why the melanocyte can not reach maturation.
So this was a big discovery for evolution in the fact that they found out it was the ALX3 protein and its levels is the reason for the different hair colors but how or why the amount of ALX3 was presented in each region of the animal is what is still unknown.