I'm naturally an ash blonde that started going grey in my early 20's. It's funny, when I was a teenager, I used to lifeguard and my hair would sun bleach out to completely white (then turn green from the chlorine). Anyway, I have a streak in the front that was always lighter than the rest of my hair and that's where I started going grey. In fact, that's the only place I'm grey now and I'm pushing 50. Well, just like someone mentioned earlier about feeling like Cruella, for me it made me feel like a skunk. So I dyed my hair to match my natural color. This worked out great because as it grew out no one could really tell the difference. Except I would see the grey and know it was time to dye again. About 9 months ago I just quit. Since my hair is so light anyway, the grey pretty much blends in so I'm ok with it now. If I'm feeling really sensitive about it, I avoid looking in the mirror or change my part so the nongrey hair shows more than the grey.
To keep my hair, both blonde and grey, bright I just use something that I got at the hair dresser that's purple or blue. But you only use a dime size amount and mix it with your regular shampoo. I also only use shampoo for blondes and something to control the frizz because I have really coarse hair with a mind of it's own. I also avoid chlorine; green hair doesn't look so good when it's wet (kinda like snot).