need non oxidizing color to cover gray

I've tried some of the clariol products to cover gray in my husbands hair. I feather it in and it's been ok till it oxidizes with yellow. This has happened with all the 'tones' that I used, blue base also. He had his barber use something that was put on his whole head for only 8 minutes, had no peroxide smell. He said it should not oxidize or turn yellow. It seemed to  just darken everything by just a bit. I'm trying to find out what this is so we can use it at home so we can do it ourselves. Any ideas what it is?

THANKS!!!

DBD