NO... just NO. The sets have their personality and that means shapes and colors. Every item was made with the witcher universe in mind. There´s a limit for customization, it doesn't mean that every game should give all options all the time.
Colors aren't merely a small thing. Designers and producers researched and found proper sets of colors that reflect the schools and history of each set, and that means something for the universe of the witcher.
Not only unnecessary, they would break the personality of the game. Everything has a limit, and if someone wants a dress to be red, is will be red. Color changing system is something very cheap to make, and if they didnt give that from the beginning, they wanna keep the items as they were meant to look like.
I think some people are treating this game a bit too seriously. Its realistic to a degree but don't forget that its a video game so its ok for it to have other unrealistic features and I'm pretty sure that adding armor color options won't take away from the experience