Office & Visual Studio stuck in 256 colour mode
I had this problem. Went into the NVidia control panel and ran the Display Optimisation wizard. After that it was fine. Had to arrange my monitors again (so they were in the right order) and set my primary display, but it was fine after that.
According to google, this problem is caused by your dual displays.
Switch one off, re-boot and try to load office again.
I have managed to fix this issues by removing any display drivers especially dual display/wireless display, and reinstalling the video drivers.