A basic function to transform a float into a RGB value (from green to red)

float2rgb.js

function f2R(f) {
  var r = 255
  var g = 255
  var b = 0
  var x = Math.abs(f - 0.5);
  var i = Math.ceil(600 * (0.5 - x));

  // range between green and yellow
  if (f < 0.4) {
    r = i
  }

  // range between yellow and red
  if (f >= 0.4) {
    g = i
  }

  return "rgb(" + r + "," + g + "," + b + ")";
}