Skin ranges in a myriad of different shades. Tattooers often have to make many color decisions after the completion of a design based on additional factors in a person’s skin. Factors like the hue of a skin tone. Even though two clients may have a very similar skin tone the palette you use on one may vary depending on whether they have a warmer or cooler hue.
In a cooler skin tone blues, cool greens, and indigos will tend to fill out better. Although you can and should use warmer colors, sometimes a “cool” red might be more applicable to the situation. Depending on the client’s skin, a warm color on a cool hued skin tone might cause some colors to neutralize, or become “Muddy”, which is the same thing that happens when you mix complementary colors on a palette or in a tube.