Several years ago my then-hairdresser very honestly said I didn't need high/low/inbetween lights as my hair was greying attractively and was doing its own silvery streaks quite nicely. So I stopped and have never looked back. Honest hairdresser having left to be a mum, the one I have now gives the most fabulous cut which complements all the grey streaks and makes me feel confident in wearing my silvery grey hair.
I had my colours done many years ago and was classed as a "true misty summer" (think Monet), and was told that the "true summer" type can go grey most successfully, so most of colours have stayed as they were pre-grey. Now though I find I can carry black more successfully, provided it's well away from my face (gap can be filled with scarf from summer colour range). Having said that, I don't follow the colour palette rigidly, but it's always a useful guide and if I walk into a clothes shop and have a quick survey of the shades on show, I know whether to stay or go. Saves a lot of time!