How would I go about return the color of the desktop background, preferably in RGB format?

Take a screenshot of it and open it in Photoshop. I can't see a way of doing it inside mIRC.

Well, that would be the way to go if I was only using it for a personal script, but I'm experimenting with an idea which uses the desktop background color, so taking a screenshot of my desktop would be kind of pointless. Besides, I could just as easily obtain the color via the desktop properties if that was what I wanted.

I thought that there might be a way of returning it with com objects, but I haven't used them before.

and what if the desktop isn't just from one color ?

Use $regread by qwerty.
//echo -a $regread(HKCU\Control Panel\Colors\Background)

Excellent, thanks.