You can't change your color if you are a goo and Sera has an event that bypasses this. I had to use the console and directly edit my variables to not be florescent yellow.
For hair/skin, it used to be you were limited to the Graneal (or w/e they're called) colors in the Deep Caverns of Myrellion. They dropped crystals (maybe you had to be in silly mode for them?) and you could apply them to your goo.
But, these days you can have Ceria (Tavros stylist) dye your hair, match your skin to your hair, and then change your hair to whatever color you want it to be. Bunch a steps but Goo don't natively have the ability to change their color on a whim even in universe. Or, at the very least, they don't show it, so that's fine.
The corrupted version is one of the few sources of any kind of perks in this game.
Most corruption perks kind of suck (raise fertility/virility by corruption/10. (Corruption/10)/3 increase to pregnancy multi. Ability to go into heat/rut once per 30 days (or twice? if you take both) and a second source of eggs.
It's not much. Certainly nothing compared to CoC and even less compared to TiTS. But, it exists.
One of us~