Cells

It is derived from the Glowing Cells image, which is already constructed to be fully uniform in the RGB space. The pixels in that image are recursively partitioned here into 8 equally sized groups, depending on whether their colour is closer to pure black, red, green, blue, cyan, magenta, yellow or white. The partitioning acts as a binary search of the unique colour to associate to the pixel, at every iteration reducing the range of each component of the colour by half.