I did that last year. We were in Spain and although I used my usual product and shade, I think the sun had made my hair porous and nstead of my usual blonde, it came out dark brown. I cried

Like yours, my hubby didnt know what to say except "Can you wash it off?"
Took me some time to get my usual colour back.
Have you got any anti dandruff shampoo - its said that a few washes with that can strip some colour out.
Ariadne xx