Here's some info: http://www.wikihow.com/Lighten-the-Colour-of-Your-Hair
Hope it helps, Good Luck !!
That happened to me once, there is this stuff iveonly ever found it at one place, its usually at places specifically for beauty supplies, but its called like red toner or something its a tiny little dropper thing and you put it in your hair and it seriosuly tones down the red in your hair, it works well. good luckHow do you tone down red hair color?
You can put a darker shade of red over it tone it down. It's hard to advise, because I'd have to be able to see your hair and know what you're trying to achieve in order to help you best. If you like the red, just want it a darker version, then find a color that is one or two number levels down from the one you used. For example, if you bought a level 7 red tone, use a number 5 red tone to darken it. If it comes out too dark, don't worry, red is notorious for lightening up in no time with your regular shampoos. Good luck.
But as always, I recommend you go to a professional.