Coloring after using Color Oops

Its actually not always lighter.  And I wouldn't go whole "levels" lighter, just a couple of shades (if you go lighter at all).

You want to use a lighter than you want shade if you are going darker, because your hair has been previously processed and will absorb more of the pigment.  (Often those who are trying to go brown wind up black and hate it because of that). 

If, on the other hand, you just colorfixed and your hair is yellow and you are going for a dark blonde shade on hair that is porous from processing, then you would pick a dark blonde one shade darker than you want to end up with because it won't hold the color so well.  By one shade, I mean the same tone of color (the one with the right base, like Rebekah said), but one shade darker (almost the color you want but very slightly darker).

Hello,