Here is a transition I made so that you can color correct 2 clips on the timeline for matching color.
With a transition, no need to make compound clips and correct in the browser, you can do it on the timeline.
This transition could probably be improved and some other ideas added... go for it..
This is for when FCPX match color dont work.
Add transition between 2 clips, stretch if needed
Put playhead over transition.
Select incoming clip and color correct to outgoing clip, or vise-verse.
Then Delete trans when done.
There are 3 panes by default but you can resize, rotate and feather the panes as needed so you can see various areas of the clip you are correcting.