New dark color in source monitor for audio background

Hey everyone!
I got the beta, and all nice and good except for a few minor things I noticed for now. When I double-click the audio file in the project window, it opens in "source" window, and now the background of the audio waveform is quite dark green color and it blends with the color of the waveform itself. in the previous versions, the background color of the waveform was much brighter and contrasty to the waveform itself.
can anyone suggest how to change that? of course, I tried the @labels@ section in the preferences but it does not affect the issue with the color I mentioned.
Thanks!