What is the meaning of the colors in the coauthor index?

The coauthor index at the bottom of a dblp person pages uses colored boxes to indicate different communities among the coauthors of a person. Communities are identified using a simple graph-based heuristic. Each community is given its individual color, and the coauthor's names are listed in the coauthor index along with a box of that color. If there happen to be singleton components in the remaining graph, then these authors are listed with no particular color (that is, "empty boxes"). Please note that due to layout limitations, we do not depict more that 25 communities.

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