
I don't think you can do that on any of the major color systems (Baselight, Colorfront, Lustre, Mistika, Nucoda, or Scratch). I think the software would have to buffer two simultaneous versions and switch between them, and that's more stress than they can take. I don't think there's enough processing power to handle two simultaneous streams of color.
One workaround would be to render out a version without that color node and play it back simultaneously as a Reference Movie.
Otherwise, we just bypass the node and look at the shot one way at a time.
You can Loop versions and use a split screen to see the differences, so that might be another potential workaround.