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I recently looked at Applying four colors theorem in polygon map using ArcMap which relates to this topic but as far as I can tell there is currently not a working plugin or script for QGIS 2.0 to achieve a four color theorem for styling polygon vector data (it doesn't necessarily have to be 4 colors, just so that each neighboring polygon is a different color, though keeping it at a minimum number of 4-6 colors would be elegant).

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3 Answers 3

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This is natively supported in QGIS 3.

  • View → Panels → Processing Toolbox
  • Select Topological coloring
  • Set parameters as preferred. Run.
  • This will create a new layer with an additional color_id column but still the same color.
  • Edit the properties of the new layer, Symbology section.
  • At the top, drop down to select Categorized.
  • Define the column as color_id.
  • Select your color scheme.
  • Click Classify to create the categories and assign them the colors.
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    As of Qgis 3.26 this does not necessarily achieve 4 colors. In my first test using the counties of NM as the input layer, the algorithm required 5 colors regardless of parameter choices.
    – Llaves
    Feb 22, 2023 at 16:24
  • @Llaves, I did check my own maps and got the exact same result with older and latest versions of QGIS. I initially tried a map that required 6 colors but it was the same with the older version of QGIS and it seems that it was required. Feb 26, 2023 at 19:59
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You could try the Map Coloring plugin. You need to enable experimental plugins in the Plugin manager to get it, and look for Coloring a map in the manager. For some strange reasons, you get a blank icon, so use Plugins -> Map Coloring -> Map Coloring from the menu.

The output looks like this, after switching to Categorized styling on the COLORID field:

enter image description here

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Use the TopoColour plugin, which is already compatible with QGIS 2.x but is not yet available in the official repository:

https://github.com/nyalldawson/topocolour

Download the zip file and unzip it in the QGIS plugin directory:

  • Linux: ~/.qgis2/python/plugins
  • Windows: C:\Users\{username}\.qgis2\python\plugins
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