Remove Color from a Potion Keg

[Firecrest]

Is there a way to remove the color or use a furniture dye kit to dye them back to normal?

 

[Delvorin]

As far as I know, the only thing that would do this is an unused furni tub. I think furni tub and regular dye tub are the only dye tubs that don't have the default option.