For me, I either
1. Use Bigen, which is designed to cover gray hair. The only drawback is that it only comes in dark shades
2. Use ColorWorks, which comes in blonde shades, which I blend with
3. Gray Magic, which is a product you can buy at Sally's, even as a trial size. The only drawback is that you may have to readjust the hair color since the liquid is a dark color.
Hope this helps