How to swap colors?

The easiest way would probably be via the floodfill tool with tolerance set to 0. You would have to click all regions with the 41,41,41 color. You could also use the Custom operation command in the Effect menu and place this code there:

var image = Document.RasterImage;
var sizeX = image.sizeX;
var sizeY = image.sizeY;
for (x=0; x<sizeX; x++)
	for (y=0; y<sizeY; y++)
		if (image.GetPixel(x, y, 0, 0) == 0xff292929)
			image.SetPixel(x, y, 0, 0, 0xffe55a13);

the 0xff...... are the color representation in hexadecimal code

Is there another faster way to do this? I remember looking through the site and finding someone linking to a script that you download and add to Realworld paint which automatically did this process.

can you explain in detail