Forked from Kai Chang
Using Lab || HCL color spaces to interpolate between two colors is better than using hsl, for example:
var color = d3.scale.linear()
.range(["steelblue", "brown"])
.domain([0, 10])
.interpolate(d3.interpolateHcl);
https://d3js.org/d3.v4.0.0-alpha.45.js
https://d3js.org/d3-hsv.v0.0.js
https://d3js.org/d3-scale-chromatic.v0.3.js