Graph Coloring

Graph coloring is when you assign colors to the nodes in a graph.

A legal coloring means no adjacent nodes have the same color:

For a graph to be colored legally, no adjacent nodes can share the same color.

The color could be used literally. Say we're coloring a map. We'll want to color adjacent states or countries differently so their borders are clear.

The color could also represent some concept or property. For example, say we have a graph where nodes represent university classes and edges connect classes with overlapping students. We could use colors to represent the scheduled class exam time. In an illegal coloring, a student could be booked for multiple exams at once!

Edge coloring is less common, but it's also a thing. A legal edge coloring means no nodes have two edges with the same color.

Last updated: June 7, 2026

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