Wait a week or two and then use another lighter shade of colour, keeping in mind that your hair grabbed the first colour and went the darkest version of the colour you picked. You can only go 7 shades lighter than what you have put on, so keep that in mind when you check the box. Call the colour advice number on the box you used and they will tell you a colour or two to pick from and will send you a voucher to buy it, too. I stripped dark brown down to ash blonde and they were very helpful to me. Don't despair, you can fix it!! Good luck.