HazeOver is a $4.99 Mac app marketed as a distraction aid. The idea is that it dims all other windows so you can focus on the content in the foreground window (a blog post like this one, a paper you are drafting for school, etc.). The developers have prepared a short demo video that shows how the app works.
While that may be a good way to use this utility, for me it has become a helpful low vision aid as well. I often have a difficult time finding the mouse cursor and popup windows if they are out of my field of view (currently about 7 or 8 degrees depending on the day). I have been using Mousepose to help with the mouse cursor problem. Even with the mouse cursor set to the largest size it allows in Mac OS, I still have a difficult time locating it on the screen, especially when I have a dual monitor setup. I have found that the spotlight Mousepose puts around the mouse cursor when I press a special key (I have set to F1) makes this task much easier.
HazeOver does pretty much the same thing but for popup windows. When one of these windows pops up on the screen, the focus is assigned to it and all other windows are dimmed. In the HazeOver preferences, you can determine whether you want just one window to be highlighted or all front windows within the active app. I find the one window setting to be the most helpful with popups. You can adjust the level of dimming at any time using a slider that can be accessed by clicking the Menu Bar icon. For the best performance, HazeOver asks to get access to Mac OS as an assistive device.
A free trial of HazeOver is available from the developer’s site if you want to try it out first before you buy it on the Mac App Store.