So I dyed my hair blue black and noticed the next day that some of my hair didn't dye so do u think I could re dye it again with the same color?

I don't see why you wouldn't be able to. Try only dyeing the area that is needed though.

You can, but it's not great for your hair. In fact, it's very bad for your hair.

I'd wait a few weeks before re-dyeing.