code: public static int toColorWithAlpha(int red, int green, int blue, int alpha) {
  		validateRGB(red);
  		validateRGB(green);
  		validateRGB(blue);
  		int color = (red & 0xff) << 16 | (green & 0xff) << 8 | (blue & 0xff);
  		if (alpha != -1) {
  			validateRGB(alpha);
  			color = (alpha & 0xff) << 24 | color;
  		}
  		return color;
  	}
docs: Convert the RBGA values to a color integer
  
  @param red
  red integer color inclusively between 0 and 255
  @param green
  green integer color inclusively between 0 and 255
  @param blue
  blue integer color inclusively between 0 and 255
  @param alpha
  alpha integer color inclusively between 0 and 255, -1 to not
  include alpha
  
  @return integer color