Colorants are substances that you apply to change the color of something else, and there are two main categories of colorants: pigments and dyes. What is the difference? It actually has more to do with the carrier solution that delivers the colorant. Pigments have colorant particles that do not dissolve or go into solution, which is technically called a suspension. Colorant molecules in dyes dissolve and form a solution.
For tattooing, we use pigments, because they do not dissolve in the body and get wiped away. We would not tattoo with Henna, for example, because it is a dye and would not last. Pigments have staying power and good fade resistance.
Pigments are mainly inorganic compounds, metal salts, with the notable exception of carbon, and traditionally come from geological sources. Iron oxide (rust) is dark red, carbon is black, mix the two together, and you get a dark rich brown. Ochre, which is iron oxides mixed with clay, gives brown and flesh-tone colors. Copper salts are typically used to make blue tattoo pigments. That’s just a few examples of pigments used in permanent makeup ink.
If you are interested in more information about pigments, see this interesting webpage about Tattoo ink chemistry: https://www.thoughtco.com/tattoo-ink-chemistry-606170
And, the Wikipedia article on pigment is worth checking out too: https://en.wikipedia.org/wiki/Pigment