OK, so about 8 or 9 weeks ago, I tried to lighten my hair, it didn't turn out right so I put a dark color back over, Now last night I got a medium brown and it turned out a brown/ orange.. would I completely kill my hair if I went and bought a dark color to go over it sometime today or tomorrow? I have conditioner sitting in my hair right now just to add some oil back to it..

6 weeks after a dye... you are able to redye your hair

Hair doesn't get better over time. It doesn't actually heal. It has no blood supply and "repair" reactions simply don't happen. If your hair is damaged enough to break today or tomorrow, it will be damaged enough to do the same thing in six weeks. There's no scientific reason to wait.

Wait, I can think of one reason -- your scalp. Oils from your scalp protect it from peroxide and dye. Waiting 24-48 hours is usually sufficient to replenish those oils.

I agree. 24-48 hours is fine.