Males tend to be clearer, but I have some that are quite red. Also, some females can be clearer. A better way to tell is to look for the saddle - a yellowish patch around the "shoulders" of the shrimp. I'm not sure but the shrimp on the left in the second pic seems to have one. If the shrimp has a saddle, it is a female.
Adult females also have thicker tails that are rounded on the bottom, while males' tails are thinner