My personal opinion (which I’m inventing right now) is that any body modification that causes irreversible changes needs to wait until you are a legal adult, but any changes that fade away or heal on their own are less of a big deal. So a teenager getting a lip ring=no big deal (other than risks of infection) while a teenager getting a lip plate would be a Very Big Deal.
(This reminds me of a time in the 1990s when I was a the beach and saw a girl who was somewhere around 6 years old walking around with what I sincerely hope was a temporary tramp stamp.)
For #1, I’d be concerned about the safety of the dye on the skin. If it’s not placed on the roots, then whatever. #2 - This is done in infancy in many cultures and that’s fine with me.
#3-6 - Somewhere around age 15-16. The others should wait until adulthood.
The objections to earrings here are really astonishing. I had my ears pierced when I was six. My sister was five. Multiple piercings – she had her double pierced in fifth grade. I was in high school, but they closed up. (Anything more than three, wait until you’re a teenager) Ears though, I don’t give a shit.
Any other type of piercings can wait until you’re over 18.
Hair dye: if it’s permanent, I’d say teens. For younger kids, non-permanent or semi-permanent dye I wouldn’t have that much of a problem.
Tattoos: I think most places won’t do it until I person is over 18.
(BTW, I think it kicks ass to women in their fifties and beyond dying their hair weird-colors. Rock on, granny)
The people saying “21” strikes me as weird: haven’t we decided that 18 is an adult? (Plenty of soldiers were fighting and dying in WWII at 16 or 17, and some countries have the voting age as low as 16).
Tattoos - the only advice I gave her was “Put it someplace that you can cover when you want or need to, and make sure it has some significance for you. Finally, wait until you are at least 25. What you think is ‘cool’ at 18, you won’t think is ‘cool’ a few years later” so says the person who would have gotten a tramp stamp because they were awesome when I was 19.
We made our daughter wait till she was 12 for pierced ears, just to make sure she was mature enough to take responsibility for them and not let them get infected. The Smaller Girl turned 12 just a couple of weeks ago, but hasn’t asked yet.
Any other piercings or body mods…I’m leaning to “old enough that I can’t stop you”. But the thought of piercing tongues or other sensitive areas just generally gives me the willies.
Hair dye, I really don’t care. School cares though. Gotta give those teenagers something insignificant to rebel against…