I recently tried the John Frieda foam to color a small amount of grey (1st time at-home ever) and I was pretty happy. A few pointers from my experience...
1. I have thick hair and it took FOREVER to get my hair saturated and it never really "foamed" up like the picture (there's a video to watch, too). By the time I had all my hair covered, my timer had long gone off. I was freaking out, but it was fine in the long run. In the future, I will have a 2nd box on hand!
2. I used "Light Golden Brown" (close to my natural color) and there was nothing light or golden about it. Luckily, I'm not too picky, but be forewarned that it comes out much darker. It's really a medium to darkish brown with a good bit of red.
FYI...I went on the John Frieda website before coloring, which was very helpful and informative, and they also had coupons that you could print off.