I went to the Aveda Institue last week for partial highlights to blend my naturally med-dark blond roots into my lighter (med ash) blond hair.  My hair grows insanely fast- about an inch a month, so I asked that she put some thin highlights through the regrowth to make retouching lower maintenance.   My platinum blond colorist dyed the whole top of my head (or at least the regrowth) platinum blond. With a distinct blue tint.  I know they're students, so I didn't make a huge fuss, plus the girl looked like she was going to cry.  

I'm coming in again today for an instructor to do a (free) correction, either tone my whole head darker, or ideally low lowlights to blend in the now 1/4 roots that look black against the platinum.  My question is, am I supposed to tip the instructor? Are they allowed tips? How much? I always tip the students $5-$10, but this seems different.