All of the custom colors found in d3.js blocks were used as input. The data was taken from enjalot’s block and includes 3250 different blocks. He parsed out hex codes, hsl(a) and rgb(a) in any html, js or coffee file found in each block and I converted all of these to 6-digit hex codes. There were 24700 different color statements in these blocks that make up 4350 unique colors. The Self Organizing Map clustering grouped similar colors together in hexagons and displays the “average” rgb value. The size of each hexagon is scaled to the number of (the 24700) colors that are present in each hexagon. The biggest one, pure black, #000000, has 1500 entries
Another version, based on a clustering of both the rgb & hsl values can be found here
A collection of blocks scanned with blockscanner for the bl.ocksplorer.org project with some further processing. Based on enjalot‘s block: block colors