code: function (startColor, endColor, count) {
  			var lightness,
  				hsl = ColorHelper.rgbToHSL(startColor);
  			if (count === undefined) {
  				count = endColor;
  				lightness = hsl[2] - 20 * count;
  				if (lightness < 0) {
  					lightness = 100 - hsl[2];
  				}
  				endColor = ColorHelper.hslToHexColor([hsl[0], hsl[1], lightness]);
  			}
  			return ColorFactory.interpolate(startColor, endColor, count);
  
  		}
docs: Sequential schemes are suited to ordered data that progress from low to high.
  Lightness steps dominate the look of these schemes, with light colors
  for low data values to dark colors for high data values.
  @param startColor
  @param endColor (optional)
  @param count