You can buy dye stamps if you don't have ESO+, but honestly unless you've only unlocked two dyes the ESO+ way is going to be a much better option.

barbarian340 wrote: »

so i have eso plus...and i currently have the assassin costume...can i dye that? even though the colors are preset?

If it's a costume in your collections UI, then yes you can dye it (I think the Mannimarco one is bugged but that's the only one like that that I'm aware of). You cannot dye disguises that you get from quests.

I dyed that one and it is sweet looking now. All the costumes look way cooler when dyed differently. Gives your charachter a real unique look in the game.