A HaXe method for blending two 32bit hexadecimal ARGB colours together. It's important that the input values are ARGB, not just RGB values. For example: 0xFFFFFFFF (32bit ARGB), not just 0xFFFFFF (24bit RGB). Credit to Mark Ransom (https://stackoverflow.com/a/1944193/2178791) and Michael Baczynski (http://lab.polygonal.de/?p=81).

BlendColours.hx

/**
 * Merges two 32bit hexadecimal colours, and returns the result.
 * 
 * @param	First hexadecimal ARGB colour.
 * @param	Second hexadecimal ARGB colour.
 * @return	Returns the two colours blended as a hexadecimal ARGB value.
 */
public static function blendColours(colourA:Int, colourB:Int):Int
{
	// Bitwise hex extraction...		
	var aA:Int = colourA >>> 24;
	var aR:Int = colourA >>> 16 & 0xFF;
	var aG:Int = colourA >>> 8 & 0xFF;
	var aB:Int = colourA & 0xFF;
	
	var bA:Int = colourB >>> 24;
	var bR:Int = colourB >>> 16 & 0xFF;
	var bG:Int = colourB >>> 8 & 0xFF;
	var bB:Int = colourB & 0xFF;		
	
	// ... blending...
	var a:Int = Std.int(aA + (bA * (255 - aA) / 255));
	var r:Int = Std.int((aR * aA / 255) + (bR * bA * (255 - aA) / (255 * 255)));
	var g:Int = Std.int((aG * aA / 255) + (bG * bA * (255) / (255 * 255)));
	var b:Int = Std.int((aB * aA / 255) + (bB * bA * (255 - aA) / (255 * 255)));
	
	// ... and bitwise re-assembly.
	return a << 24 | r << 16 | g << 8 | b;
}