Question about hair dye?

[riserchristine]

Hi! I have a question about ammonia-free hair dye. Is it safe to use on a teenager? Like is it really bad for your hair and/or does it kill brain cells? I'm a male and I dye my hair maybe once a year. Also, is it okay to dye your hair when it's really short? I just cut my hair short for the summer, and I was wondering if I should wait for it to grow a little. My front and top hair isn't too short, but my back and sides are.
Also, how would Dark Auburn look on a male with black hair?