My Liyure is Gold and Silver. I dyed him that RIGHT before the Trance Potions were released. If the Trance Potions had been released before I did that, I would have just gotten a Trance Potion and used that on him rather than the G&S Dye Kit. I would LOVE it if there was a way to redye your pet without the other color going to total waste. So, I have a couple of ideas as to how we could do this...
Color switch. A place on one of the planets that you could take the pet that you want to dye and the pet you would like to switch the current color to. For example, I want to dye my magenta Ezahni azure. I would grab a pet with no color and take them both to that area and it has you select the pet that you would like to dye, the dye kit you would like to use, and the pet that you would like to switch the color magenta to.
Return. When you dye a pet, the bottle goes to a place (attached to your pet's profile) where you cannot sell/trade or move the bottle from your account in any way. If you sell/trade the pet, the bottle remains on that pet's profile). If you choose that you no longer wish that pet to be that color, you can resell the bottle back to the Black Market for half price and it takes the color off your pet. That way, you do not get ALL of the TU back, but it is not a total loss if you wish to change it's color.