Hair color is not an exact science. Even the colorist who has been making you ash blonde with platinum highlights for many years--okay, not THAT many--can accidentally make your hair yellow.
I know, because this happened to me, and despite two rounds of toner, I still look like Tweety Bird. And now I'm out of town, so the HIGHLY SKILLED colorist who accidentally made my hair bright yellow can't do anything else to fix it. (She really, really is highly skilled--I'm not being snarky at all because I have a YELLOW HEAD.)
It doesn't seem prudent to walk into someone's shop who's never done my hair before and ask for color correction, so I'm stuck until I can get back home.
The worst part is, I think all the chemicals have effected my brain. I can't seem to string two sentences together. Everything I write I end up tossing the next day. I'm either brain damaged, or just in such a foul mood over what I see in the mirror I can't function.
Either way, I'm on the verge of heading to Walgreens for some L'Oreal.