I decided to ask someone trained in this, my hair stylist from California, the woman I miss dearly (my hair stylist here in Michigan is good, but she just isn't Shannon), and if I could afford it I would really, truly fly to California every 6 weeks to see Shannon. She is that nice of a person and that good. Shannon Ely works at Salon TM2 in Irvine, if you go and see her tell her I say hi! While Shannon isn't specifically a colorist (she does other stuff too), she does good color, one of the reasons I love her so much!
Here's what Shannon had to say:
The over the counter hair color has come a long way and if you are truly using it as directed it shouldn't be causing the problems your stylist is saying it does. However, if your hair is damaged, breaking, splitting, and not shiny then there is clearly something wrong.
What I tell my clients that insist on coloring themselves is to choose one shade and stick with it. Changing the color leads to unattractive "banding". Also, try to stay within 2 or 3 levels of your natural color. Anything more and you're likely to get into some trouble. I never recommend bleaching on your own. Please know, we stylists pay a lot of money and invest even more time in learning how these chemicals will effect your hair. I like to believe I know more than a box.
Do you have a question? Make sure you ask it! I'll address questions in my Ask a Beauty Blogger post series.