Ability to automatically dim secondary monitor when focus on primary Is there a 3rd party app or combination of system settings and scripts that dims a secondary monitor until focus is brought to a window displayed on it? I like having multiple monitors but I would work better if there were a strong contrast between the two, where the contrast would invert based on which monitor had focus. (I can and do manually adjust the brightness when I know I won't need anything on the secondary monitor for awhile).

Running El Capitan with primary of a Thunderbolt display and secondary of a Macbook Pro.

I have looked at questions such as
Show a screensaver on a secondary display and
Adjust brightness of secondary display and have a sense that some of the tools might, with a additional scripting, get me close to what I'm looking for, but I am hoping someone has already solved this specific issue.
I started using the free app HazeOver which dims all windows other than the one with focus. The new beta version has a preference to dim all windows on a secondary monitor, and it gives me exactly the functionality I need. You can also opt to not dim windows that belong to the app in focus.  (I paid for it, which just removes messages encouraging you to purchase it).