Most of my useage of this revolves around the color correct node. I like to use it to separate colors and it’s a super handy way to kill those small color shifts in skin that you can get from too much drag brush. I’m always using too much drag brush.
Pick the average skin tone, then use the gain to make the skin evenly gray–like 0.5 on R, G, and B. With that done, wind the saturation up to 500 and the colors will all be super visible. use a CW to kill the unwanted ones, then pass the shot back through an inverse of the saturation, then through another one that inverts the gain and viola, you’ve gotten rid of those weird colors you didn’t like.
You can also use offset or individual contrast for your balacing, but do each one in it’s own node because you can’t invert the order of operations in the CC.
The “Look” node is also good for these sorts of escapades because it has a built in “invert” and offers more intuitive controls.