When creating thematic maps in ArcGIS or QGIS, thematic coloring (choropleth mapping) is a common technique where different regions are colored according to their data values, revealing spatial patterns. Recently, our management requested integrating this functionality into our business system. While we could publish pre-rendered maps from ArcGIS/QGIS through servers like GeoServer, this lightweight feature doesn't warrant heavy infrastructure. Instead, I explored coloring GeoJSON features directly and discovered colormap - an elegant solution.
