My hair has a lot of grey in it and I get it coloured dark brown every 6 weeks or so. I last had it done 3 weeks ago and some grey is showing through at the roots already. I wont' be able to get to the hairdresser until early September. I don't want to use a box of semi permanent colour but is there anything else anyone would recommend - like a rinse through product that would give a bit of temporary cover?