With my installation of Lightburn, currently 2.1.03, but this was present on older versions, the progress bar is a light gray when running the material test. I personally find it difficult to see, so I check the numeric portion of that information. My question is this color part of the code in Lightburn or is it a problem with my installation/computer?
I have noticed mine is gray when I have another window open. It indicates the Lightburn design window does not have the Windows focus. I see the same thing in your image.