RCS color depends on a lot of variables, just like fish they can stress out and their color washes out. A proper diet of both animal, and plant protiens are essential for them to produce a vibrant red color.
I have taken slightly red shrimp from one of my tanks, and transferred them to another tank only to see their color really "POP" in their new environment. they like to be in the plants, and able to hide from predators.
I believe, and this is only my opinion, based on what I have seen, Most shrimp have the potential to be very red, if given the right environment and diet.