I'm not a hairdresser, but i think red is hard to shift, and you can't lift tint with tint. You could use something like Colour B4 to strip the red, but it is really drying. If you have the time/money, I'd go pro.
Hmmm, the fact that it's gone red makes me wonder if it's not dye that's left. I think that a bright blue may have contained a fair amount of lifting agent and actually what you're left with is the lightened hair after the tint has faded. Bold colours in general don't hold well.
I'd be tempted to do a strand test to see what happens.