Hair Color/Bleaching

At what age would you let your child start bleaching/dying their hair? Would you limit the color or let them do what they want?

My friend is catching a lot of grief for allowing her 10 year old to have blonde highlights. Her kid has been begging for blonde highlights for 2 years now, and she made sure she knew how to take care of it to prevent damage. She also talked to her about self-love and made sure she wasn't wanting the blonde because she thought she wasn't pretty without it. I personally see nothing wrong with this.

I've decided that around 10 I would start giving my kid more freedom of expression when it comes to their look, as long as it was safe and healthy.

What do you guys think?