Why does it seem like most girls over 18 who die their hair unnatural colors are immature for their age?

There aren't any "girls" over 18 (years of age).  The average is age 12-13, but can be as young as 8 & as old as 17.  From that point, they are WOMEN.  Your wholly anecdotal assumption has no validity.     

"Ron"  If you butt hurts, fruitboy, then stop giving yourself to be sodomised so much.

Go back to fellation.  It's alleged you're pretty good at it.  

I saw a lady over 70 that had her hair died pink. It doesn't make you immature!

They "dye/color" their hair. They seem immature to you.

Age 18-20 is a transitional time, but after that, a girl should be shopping for cemetery plots and playing bingo.

trends happen old ladies used to die their hair purple thats where it all started