Parenting - Letting Go

Rose had a sleepover before the school dance last weekend. She and her friend came bounding down the stairs...all chipper and happy. They were going to dye Rose's friends hair, could they dye Rose's too?
This has been simmering a long time. The kids "nowadays" (love saying that, makes me feel like such an old codger) change their hair color with the cycles of the moon. Rose has been asking me to color her hair. I know I have a non-neutral eye, but her hair color has always been lovely to me so I always deferred.
But I knew something like this was coming. And, after repeatedly giving her all the dire warnings, and then letting her hear it in a phone call with gal pal professional hair colorist extraordinaire, she chose to dye her hair. The goal was blond top, black underneath. And friend's hair was black top, blond underneath. I was cringing inside. But you know what? This sort of stuff has to happen. We can rant and ramble and lecture and 'model' behavior, but there are just some things that kids need to figure out on their own. It is not always the same thing... my daughter happened to have hair coloring as her venture out of the safety net this time.
I did not say no. I told her possible consequences, and that I would kill them both if they got dye on my new bathroom floor... and then let 'em go.
The color turned out orange in spots, bleach bottle blond in a circle on the top and uneven. She was a bit traumatized. But not in a bad way.
When her friend had fallen asleep under her own black-purple new hair, Rose came back downstairs. "Why weren't you a strict mom and absolutely forbid me from doing this if you knew it was going to be turn out orange and splotchy?" We talked about learning things for yourself vs. hearing something over and over again and it not making sense. We talked about choices. It is hard for me to let them figure stuff out on their own, when there are unpleasant consequences. This was a very very gentle consequence, one that was traumatic (for a dramatic teen), but not permanent nor dangerous.
The next day we got a brown hair dye. That night, they went to the dance and had a great time.