Do RCS change color when they molt?

Against all odds, I've had a few shrimp living in my tank for almost a month now. I bought four of them at a local fish store. The salesperson told me they were RCS, but I'm not sure.... They were very tiny when I first brought them home, little more than babies, and they were more clear than red. Somehow at least two of them (maybe three) are still alive despite sharing the tank with an assortment of 32 tetras. The shrimp like to hide in a bushy bunch of Didiplis diandra, and sometimes they even make their way up into a huge clump of floating Water Sprite. They have grown quite a bit larger since I first brought them home, and I've found a few discarded exoskeletons at various times. Sometimes I won't see them for a few days, and I'll assume they died/got eaten, but then they'll turn up again. I seldom see more than two at a time. (That's why I'm not sure how many are still living.) Sometimes when I see them they look clear. Other times they look dark reddish brown. Do you think I have two different kinds of shrimp, or is it normal for shrimp to be clear after molting?