Final answer:
For covering unpigmented hair on a salt-and-pepper head, the color formulation should be lighter than the natural level to achieve an even, natural blend and lessen the contrast.
Step-by-step explanation:
To cover unpigmented hair on a salt-and-pepper head, the color formulation should be lighter than the natural level. This is because unpigmented, or white, hair lacks melanin, which is the pigment that gives hair its color. When coloring such hair, it's essential to use a formulation that can penetrate and deposit color effectively. The goal is to achieve an even, natural-looking color blend throughout the hair.
Colorists often opt for a lighter shade because it provides a less stark contrast against the white hairs, which could otherwise appear too pronounced if a darker shade were used. Additionally, using a shade that is slightly lighter can result in a more youthful appearance and a softer transition between pigmented and unpigmented strands.