Darker hair is harder to strip completely, and usually goes through a brassy stage before you get it to go blonde. You could try stripping it a second time, but you will risk doing more damage to your hair. You can tone it, using a cool toner, but your hair will be darker after it's toned.
Honestly, if you have dark hair, and want to get to blonde, you should have a professional do it. Home hair coloring is best for one or two shades of variation, which they usually show you on the box.