Should I use a special shampoo for graying hair?

[teaandbiscuitsface]

I've got a fair bit of grey hair but it's still fairly dark underneath and at the back of my head. Can I use one of those shampoos that enhances the grey without buggering up the non grey strands?! Cba dyeing the grey!

I use purple shampoo (Fanola) on my greys if I think they’re starting to look a bit yellow. It brightens them up, and has not noticeable effect on my brown hair. Only once every couple of weeks or so. The rest of the time I use whatever shampoo I fancy.