In terms of the quality of the glass, it seems to differ from one line of scopes to the next. I've used the Accupoints and the 1-4x didn't seem as clear as the 1-6. The Credo scopes are also very nice. If you're buying from a place like Eurooptics, you'll get to check it out before deciding to keep it. Just pay attention to things like the eye box at min and max magnification. The eye box is why I chose to go with a Razor instead of the Credo.
Choosing what color to go with will depend on the power source of the illumination. If going with something battery powered, where you can direct control over the brightness, just pick the color that you like best. Most prefer green, but I like red because it provides the most contrast for me. That color doesn't occur in nature, or at least where I go, it provides the contrast I need even at lower levels.
If the power source is gonna be fiber optic, the problem is that the reticle will turns different shades when the brightness of the light source changes and many of those shades blend in with naturally occurring colors. Although all of the colors are subject to this, amber is the worst, green is a step better and red does the best. For me, anyway. Having red and black reticles has rarely let me down.