Even better would be to take the full data set of all the survey responses, and use it to generate the partition of CIELAB space, instead of just using the single set of coordinates per name that Randall generated from those. But it would be more work.

Edit: do note they’re using a more complicated distance definition such that a straight Voronoi diagram in CIELAB space is not quite the same as their result. But the difference is so slight as to not matter, so your suggested solution would be substantially better than theirs.