Here's a (horribly ugly) proof of concept on the HUD. There's no way to turn it off or adjust it's size/position/opacity from in-game and it's permanently stuck on top of all other windows, but it's click-through and shows the basics. Just drop the files into your custom UI folder, delete them when you're done looking at it. (Trust me, delete it.
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It should be fairly easy to set up a hotkey to toggle it on/off by integrating it with another window (which will also fix most of the other issues, may even be able to get opacity control on it), once the design is finished.
Edit: Looks like the group color thing isn't going to work at all.
Just checked and none of the dynamicdata is active, so there's no way to pull color.