Well you could wait 24 hours. But I would seriusly condition the crap out of your hair because its not healthy and your hair will fall out. So if you want to die it asap then you really have to make sure your hair is healthy before and after
I Dyed My Hair But Don't Like The Colour, How Long Do I Have To Wait Before I Can Dye It Again?
You should probs wait 2-3 weeks or something..... Because if you dye it too early your hair could fall out.