Give Me Colors
https://observablehq.com/@makio135/give-me-colors
D3js diverging interpolator
https://www.geeksforgeeks.org/d3-js-diverging-interpolator-function/
color = d3.scaleDiverging().interpolator(d3.interpolateRainbow).domain([0, totalGroups])
color = d3.scaleDiverging().interpolator(d3.interpolateSpectral).domain([0, totalGroups])