For the best gray coverage, the color should be at level _____ or deeper, using at least _____ volume developer.

For optimal gray coverage, using a color level of 7 or deeper is essential, as this provides sufficient pigmentation to effectively cover gray hair, which tends to be more resistant and lacks the pigment found in naturally colored hair. Levels 6 and lower may not contain enough depth to fully mask gray strands. Additionally, a developer of at least 20 volume is ideal for achieving this coverage because it lifts the cuticle enough for the dye to penetrate the hair shaft while providing adequate processing for the color to develop properly. Lower volume developers, such as 10 or 15, may not provide the necessary lift and can result in insufficient coverage, especially for stubborn gray hair. A 30 volume developer is typically too strong for gray coverage in this context, as it is generally reserved for blonde shades or lightening rather than for gray coverage. Thus, the combination of a level 7 color with a 20 volume developer is considered the most effective choice for achieving full gray coverage.