So I'm not very happy admitting this but I have some gray hair.  I've been randomly finding them since I was in middle school but now they've deciced to clump together a bit on one side of my hairline.  It's fun.  Even though everyone tells me that it's not noticable (thanks to my light blonde hair color), I ALWAYS notice it and it drives me nutso AND the grays tend to grow in a bit thicker so they stick out even more!  UGH.  Anyway, I was lucky enough to try out the TouchBack marker specifically designed for gray hairs.  I tried out the lightest blonde shade that they offer, Golden Blonde, and even though it was a bit darker than expected, it definitely did the job.  Every morning for a week I washed and blow dryed my hair as usual and then applied the TouchBack using the little comb that combs with it - which prevents the dye from getting on your scalp and helps separate the hair so that you can see all the grays that you want to cover.  I LOVE this and it's really a great option for when you're trying to stretch out the time in between root touch-ups.