Coloring

A coloring of plane regions, link segments, etc., is an assignment of a distinct labeling (which could be a number, letter, color, etc.) to each component. Coloring problems generally involve topological considerations (i.e., they depend on the abstract study of the arrangement of objects), and theorems about colorings, such as the famous four-color theorem, can be extremely difficult to prove.

REFERENCES:

Eppstein, D. "Coloring." https://www.ics.uci.edu/~eppstein/junkyard/color.html.

Saaty, T. L. and Kainen, P. C. The Four-Color Problem: Assaults and Conquest. New York: Dover, 1986.