I have about 10 very obvious white hairs right at the front/middle of my hair (and less obvious ones elsewhere, I am not luck enough to have escaped with just 10). I get my hair dyed with semi-permanent dye by my hairdresser (she says it is quasi-permanent, but I would feel an idiot describing it as that) and that means that I don't get terrible roots. However it does wash out of my stubborn, obvious grey hairs relatively quickly and well before the rest of it needs redoing. Is there anything I can get that can just be put on that little section, without wasting an entire pack of dye? Preferably something someone else has tried and works!