Without bleaching my hair, how long will it take for Splat hair dye to come out?

I don't particularly use Splat so I don't really know the fading rate. But if you use shampoo with sulfates and warm water it should fade pretty fast, especially on black hair. You will have a magenta-ish highlight for a while though...or maybe that's just what happened to me because I dyed black on white so it faded to grey then I dyed pink...So black probably wouldn't have such a vibrant effect for that long.If you want a pink tint for just a day use a spray-on color.And no, without bleach neither Splat dye or spray-on dye will harm your hair. The warm water however, might.