Cherry shrimp will need a little time to get their color back. Much like a stressed fish loses its color on the trip home from the pet store, the same can be said for most invertebrate. However, in my experience shrimp take a while longer to regain their color. I've found shrimp in my canister filter that had turned almost completely clear but were vibrantly red when in the tank. The color does come back.
As for sexing, I haven't the faintest clue. I've always bought several at a time for better odds of mating pairs. You'll know the females when they develop eggs. Their underbelly will have a yellow mass that, if you look closely, is actually a cluster of eggs. The males will then fertilize the eggs. Keep a clump of java moss on a piece of driftwood to give them a safe haven and some natural food, (the algae on the moss, not the moss itself). They will breed in given the proper conditions.
Hope that helps