Your hair changes color as you age. I was born with blonde hair which didn't start getting darker until I was in my 20's. I would keep chemicals off your hair as long as possible. In my opinion, 14 is too young.
14?! 16?! WOAH, buddy. Everyone on here is being a LITTLE crazy. Hair damage is completely unimportant, first of all. Maybe not BLEACH your hair... but dying is just fine. Hair damage is very real today, but not the end of the world. As was said a while back, it isn't permanent. Hair does grow back, and healthy hair can be redeemed. Not to mention, it's not dreadfully common for peoples' hair to be damaged too badly if the dying is done correctly. There are worse things out there that a girl could do than dye her hair. A LOT less healthy things are done every day self-consciously. Curling your hair "damages" it. So, it's not that bad. Not to mention it helps to express personality.