Background color in full screen view

The first time I used full screen view in the newest upgrade of DTPO (2.9) it was set to neon-green text on a black background, like the earliest word processors.

I have repeatedly changed the background color and the text color in Preferences, and the text color (black) seems to stick, but a light background color doesn’t, so now both are black and the text can’t be read.

Am I doing something wrong??

Which version of OS X/macOS do you use?

EL Capitan (OS X 10.11)

Do you use the latest versions (DEVONthink 2.9.1, OS X 10.11.6)? Because I can’t reproduce the problem using these versions.