code: function getRandomLetterColor() {
      // Reset index if we're at the end of the array
      if (currentColorIndex >= colorKeys.length) {
          currentColorIndex = 0;
      }
      
      // Get current color and increment index for next time
      var currentColorKey = colorKeys[currentColorIndex++];
      
      // Return most satured color hex (a700 or 900)
      var color = colors[currentColorKey]['a700'] || colors[currentColorKey]['900'];
      
      // Invalid color saturation value?
      if (color == undefined) {
          // No saturation for black or white,
          // so return the next random color instead
          return getRandomLetterColor();
      }
      
      // Return current color hex
      return color;
  }
docs: Returns the next Material Design color for the icon background