There's no description of the image beyond the caption, so all I can do is guess. I don't think there's any significance to the colors beyond four-color theorem: you can color any map using only four colors and have no two adjacent regions the same color. The regional boundaries outline a portion of land wherein the approximate population is equal to the population of Canada. This aptly demonstrates the population density of some portions of the US;e.g. there are two Canadas in new England, one in the San Francisco bay area, but it takes all the plains and Rockies to make a Canada.
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The Master said: "It is all in vain! I have never yet seen a man who can perceive his own faults and bring the charge home against himself."
>Analects: Book V, Chaper XXVI
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The Master said: "It is all in vain! I have never yet seen a man who can perceive his own faults and bring the charge home against himself."
>Analects: Book V, Chaper XXVI