Yes, mine wash out. They never last as long as they say they will on the packet though. It's supposed to last six weeks but I'm lucky if it lasts a month. But if you make a mistake with the colour, all you need to do is keep on washing it I suppose.
I can't really remember*soontobe*, surprising what a difference 30 years makes I think it went over a couple of months, a combination of hair washing and growing out. It was very short.