I use to go w/the light browns w/the blond highlights (like the box shows), but my hair rarely came out like the box color. I'm lucky I never had a green mishap
I have used the highlighting kits in the past, but found the brush on type was messy and the ones w/the cap - it's better to get someone to help you, but mine always came out more like my hair was frosted. So even though it's sometimes expensive to get the coloring, foils, etc. done @ a salon, I prefer it because as long as the hairdresser is good & knows what they are doing - you know it will be done right.
Bummer about the gray, I'm fortunate where I'm in may 40's and still none. But my hairdresser is funny, when I go for coloring, etc., she will look for them.