When I went to pay (50 bucks), the girl who colored my hair was standing right beside me. Even though I wasn't going to tip -- I mean, I wasn't pleased by her, the highlights sucked (and were unfixable unless I wanted to dye my hair brown), and I didn't care for the school, I felt obligated to because she was staring at me. I gave her five bucks. Would you have tipped?
Oh, by the way. The 44 foils she put in my mid-length hair took 4 hours. I sat in a chair from 12:30 to 4:30.