Want to stay gray.. But need to meld old to new!!

I'm tired of coloring my hair. I am about 1/3 gray.. Dark salt and pepper. I have brown tones because of coloring but my natural uncolored hair is about 3 inches long now. All over, my hair is down to my mid back. I really don't want to cut my hair. How can I make the difference between the browns and the salt and pepper less noticable? I'm not familiar with alot of the new products out today. I've always just used over the counter hair color. Any advice would be very helpful. Thanks. Laura