I dyed my blonde hair red last week with permanent dye. My question is, I have some manic panic red passion, so could I use that mixed in with my conditioner to brighten the permanent color as it fades?
Yes, and semi reds actually last a lot longer than permanent reds in addition to being brighter.
Most permanent reds have brown bases, though, so you'll only be able to brighten it so far because you'll still have the brown base underneath.