I naturally have medium brown hair with reddish high lights to it... I thought I'd cheap out and get an at-home dye kit, which normally is fine, because typically I go darker with my hair. I thought I'd do a dirty blonde, or light ash brown, but instead of blondish brown, it's orange... what can I do to fix it?

OK, I know this at first will sound really stupid but just try it. If there are beauty academies anywhere near where you live, try going in and getting it fixed for free!! I did it for a haircut and saved $80!! I know that they are learners but they are trained learners not just a babies with scissors.

If you have a dark base already and it has red tones to it you needed to lift it woth a high lift tint - and watched to process - you can take it off any time you want to and not the desired length the instructions tell you... to put it right you should really need to go to a hairdresser hun - or buy just a toner and nutralise it yourself... toners are like a wash in wash out but if your hair has become purous then it will grip to it a bit longer - good luck

Dark hair has a lot of red pigment in it and if you apply a single process permanent color on dark hair, it will result in a brassy red or orange shade. If you want to go from brown to blonde without the red/orange shade, you must first pre-lighten your hair and then apply your desired color. You should consider having it done professionally.