If you’re having trouble with grey coverage on levels 5, 6, 7, check out this tip shared by Derek Piekarski, North America Signature Artist for Coty Professional Beauty.
Choose the /71’s as an easy starting tone to add depth to grey coverage. The /7’s have been optimized to be a truer warm brown, and the /1’s have been optimized to add more ashy depth tonality.
These two together give the best starting benefit to simply add tonality to grey coverage levels. I keep the grey coverage level target the same, but I add a target shade one level lower (but still less than half of the formula) to add more depth.
So, if my previous formula was 70% 6/0 + 30% 6/71, my new formula would be 70% 6/0 + 30% 5/71, which helps to add more tone and depth for gray coverage.