Want to Return to Natural

This is a great site, I will recommend it when I hear of anyone having hair problems. My question is what is the best way to return to my normal salt & pepper. I am a young 42, I started going grey when I was 14. Approx 6 yrs ago I started by having lowlights and then gradually progressed to permanent color. Currently, my hair has a blond permanent color and the roots are the natural salt and pepper. In order to blend the roots and continue growing in the natural color I have tried highlighting and also semi-permanent blond colors. This works okay for approx a week or so the color does not stay. I am tired of the blond, I agreed to blond because we thought that it would be the easiest color to match to the grey. My hair is very thick and grows very fast. I am now wanting to color my own hair. Need advice! Thanks!