How to highlight opencv python popup outline?

Question

OpenCV

https://drive.google.com/file/d/1RZ90wzJfTLn3xUbMy...
(why can't I attach a picture in a normal way)

How to highlight the popup I'm interested in using opencv python? The problem is that the window in certain places is very similar in color to the background, such as on the left side, when masking on a gray image, to get a binary image, in addition to the window, a lot of extra is highlighted.