pass through function for color fill instead of just array

[kernant]

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[JustinGOSSES]

Resources for later:
https://stackoverflow.com/questions/41848677/how-to-make-a-color-scale-in-d3-js-to-use-in-fill-attribute

https://github.com/d3/d3-scale-chromatic

The fill variable is currently
fill: Array(1) [ 0: Object {curve_name: "RHOB", fill: "yes", fill_direction: "left", cutoffs: Array(3), fill_colors: Array(3), curve2: ""} ]
and takes string....what will need to be changed for it to also take a function in place of the string like:
var colors = d3.scaleQuantize() .domain([0,50]) .range(["#5E4FA2", "#3288BD", "#66C2A5", "#ABDDA4", "#E6F598", "#FFFFBF", "#FEE08B", "#FDAE61", "#F46D43", "#D53E4F", "#9E0142"]);