Son's blue hair didn't come out!!!!Help!

my 15 yr old son went to salon to go from great virgin brown to shocking "smurf" or royal blue! Came back with "dark" hair with hint of violet and grey highlights.... Bleached hair to pale yellow (white with baby hair at crown) and then used basic blue base with a touch of violet to cut out any remaining yellow. Just didn't come out blue. We have 2 days before he heads off to his important camp and we are going in "to correct" today. Any thoughts on next step. I gave my son the freedom to set this up. I didn't have a clue the salon has NEVER done blue before!!!! Please email me at annette.a.smith@tek.com with any suggestions... Thanks.