You might want to have a look at these tools:

http://freedesktop.org/cgi-bin/viewcvs.cgi/svg-icons/utils/svg-utils/

They were used, for example, on the Lila icon set to have a blue and purple version. They can also do a lot more, if you have a good look.

A big part of this app is figuring out what to change the colors to, which could be accomplished by putting that library together properly, but at this point, that would mean learning python (on my todo, but low priority) and recoding the whole thing.

As a note on the algorithm used, the theory is that the individual colors chosen is not important- just the distance around the colorwheel- so it simply does a hue rotation.

Though, for the next major version upgrade, I probably will switch to that library. Right now, it decides what the main color is based on the number of occurances, which means if you have a dozen small green triangles and one big blue circle, it decides green is the main color. I want to change it so that it finds the shape with the largest area, and uses that as its main color.

Ah, OK I see. That's an interesting idea.

You should contact the author of those SVG tools on fd.o, since he and I are working with freedesktop.org towards some cross-desktop SVG tools. He'd be interested in what you're doing, and you could develop your tools as part of the fd.o project:

http://www.programmer-art.org/?page=contact