Its simple. If you have an accessory like Regal Vertical Vents, you could pay a reasonable sum of ce or cr to have it recolored as one of the common colors(Dusky, Military etc...) I'm not sure if this could apply to skins like Shadow or the event skins but meh...Another thing is the fact that I'm assuming players already paid for the item and are willing to pay more to have it reskinned. This could apply to accessories already equipped or in your bag, this would be a plus if you got a Skolver Cap from auction with Valkyrie Wings, but oh wait, its the wrong color and your willing to pay an extra 50kcr or 100kcr to make that expensive item useful.
UPDATE : This does NOT apply to Volcanic/Prismatich and extremely rare color schemes. ONLY common ones that are easy to obtain.
List of color schemes that could be bought with cr/ce...
Cool, Dusky, Fancy, Heavy, Military, Regal and Toasty.
Sadly, it might become exploitable if the players didn't have to equip the accessory to change it's color. This could end up with multiple accessories that shouldn't have color scheme.