It's not exactly what you're looking for. Basically it's an online swatchbook and it also gives you suggestions for using the color. (Ex. Supergel #93: Blue Green [darker] Useful for mood of mystery and for toning scenery that has been spattered in blues.)
Different gels will look different on everyone. A pale person will reflect certain colors a lot more than a tanned person. I think that's more of a case of trail-and-error.
As for moods. In all honesty I just do it in my head. The problem with using color in a light design is that the audience tends to automatically jump to conclusions. If they saw someone being bathed in pink light they'll start to think that that person is falling in love, that kind of thing. The website above may help you some.
A nice program you can test out at http://www.westsidesystems.com/vll/vll.html is the Virtual Light Lab. The Demo version gives you two lights and a gobo and you can test it out on a sphere. You are also able to adjust the cyc colors. If you buy the program you get something like 72 lights or something. Anyways, the demo version has been fine for me.