Don't understand your problem. Be more specific or show example of "colour is messed up."
On my CS6 system, the Contact Sheet II plugin works fine. In the dialogue you can specify the output colorspace, and when you feed it images in different colorspaces it does the conversion correctly as needed. Can't imagine a way to screw that up.
I doubt if it matters, but are you Mac or PC? What version of Photoshop? Are you feeding it Tif, jpeg, or PSD? What colorspace is the input, what colorspace is the output?
And for what it's worth, I find the contact sheet function in the free FastStone browser a better choice. Mostly because you can save presets. One for portraits, one for landscapes, different sizes, etc.