This is a simple weakaura that only loads in Spires of Ascension (all difficulties) that puts a square over your entire screen (underneath your UI etc) that is a translucent orange-brown color, sort of like a weakaura version of f.lux.
You can change the intensity by going to display > color > then change the alpha value on the right hand slider.
If you accidentally drag the weakaura out of place, a good way to reposition it is to change the alpha to 100 (so its a solid brown rectangle), reposition it, and then set the alpha value back to whatever you feel is comfortable.
You can add the zone ID for other instances or zones if you find other areas too bright blue as well.