An additive color blending algorithm in 10 lines of code that blends colors while retaining the brightness of each color to create realistic blends.

color_blender.js

/*
  Pass in 2 colors {r1,g1,b1} and {r2,g2,b2}
  Select bi the blend intensity of the first color (0-->1)
  Output is in form {r,g,b}
*/

var blend2A = function (r1,g1,b1,r2,g2,b2,bi) {
  var endR = bi*r1+r2*(1-bi)
  var endG = bi*g1+g2*(1-bi)
  var endB = bi*b1+b2*(1-bi)
  var scale = Math.max(Math.max(endR,endG),endB)/((2*bi*Math.max(Math.max(r1,g1),b1)+(2-2*bi)*Math.max(Math.max(r2,g2),b2))/2)
  var endR = endR/scale
  var endG = endG/scale
  var endB = endB/scale
  var blendArray = [endR,endG,endB]
  return(blendArray)
};