short answer: yes.
long answer: yes, but it wont go back to your original color.
I have used color oops twice and have been satisfied with the results. I have brown hair and i tried to dye it darker and it came out WAY DARK, like black. I used color oops and it lightend my hair to a med/light brown.
I would say, it would be good to use, if you intend to recolor your hair to another shade because there is really no guarantee of how much it may lighten your hair.