I've only had my RCS for maybe 2-3 weeks, and I've got a pregnant one already!! They were tiny when I first got them, but they've grown fast and I guess they're happy - since they're procreating...lol. Anyways, I just thought I'd share the happy news...lol.
Usually RCS males are clear or have very little red. Maybe you have all females in your tank? That can happen if you get them at a LFS since they don't want to carry non red RCS.