Clear dye
That would be rather amazing, provided that people do not begin to abuse that option and end up running around naked.
I don’t even see a problem with people appearing to run around naked since you can’t take off the default underwear anyway. Even then, it would be a simple matter to limit which things you can dye to a clear color. I just think clear dye would open up a whole new level of customization to gear appearances and I think I’m aligned with many others in loving the ability to customize my character.