Due to a new discovery, I've decided to bump this topic with a bit of useful information!
I've looked into it upon stumbling across it, and I have confirmed that it's possible.
You can add extra colors onto the player palette!
That's right! Want your own set of team colors? Or maybe a new color that stays the same on every team? Not a problem!
Simply go into your palette file and add the new trio of colors onto the end!
Be sure to move the see-through shield column so that it's on the far right!
With this, you can add up to 22 new colors to your palette, making for a total of 30 COLORS!
I've personally tested this out, and I can assure you, it does work! Exceeding the 30 colors, however, doesn't cause a crash or anything. It just doesn't change the skin color to whatever's below it in the palette.
Enjoy this new discovery and feel free to put it to use for mods and graphics pack if you want!
(Although I don't see why anyone would actually need 30 colors...)