I'm still rather new to this site and don't understand all the features, and I want to know if there is a way to give my avatar a custom skin color?

Is it possible to do it, like enter in a hex code? Or am I stuck with the clickable colors only?

Nope, only the colors listed in the wardrobe and those you can get from wearable items, like these:

Aw. Well, at least it answered my question!

If you hang around for morostide (our Halloween) you can zap for new skin choices. Also going to Subq will randomly award you the lace skin. But these are more modification than color options.

I know about the mods! And thank you for letting me know about the lace skin!