B..
My fiend has dirty blonde hair, and she started graying as well. (She's 26!!!) Her colorist does a deep treatment every once and a while to help keep the hair healthy. She also does a gloss to keep the hair looking healthy. I should add, she doesn't do an all over dye. She said that those with very blonde to dark blonde hair don't need all over color to cover the grays. She does an all over highlight, and it's much easier on the hair. I have also heard hair holds onto highlights and low-lights better then dye. I have never noticed a gray on my friend, so it must work!! She said her hair was about 40% gray before I met her, and I can't believe it!!
As for me, I don't know what I will do. My mom is 48 and just now getting some grays. She has very dark hair. I am a blondish color, so hopefully mine won't be noticeable. I like the color of my hair and haven't done anythings chemically to it in almost a decade. If/when I start to gray I will probably do the all over highlight.