Am 18. Oct, 2020 schwätzte Mike Bushroe via PLUG-discuss so:
moin moin Misha,
Awesome. That worked. Thanks!
Avoided the problem tonight by using convert from ImageMagick to create
the images and only using gimp to review them :).
> Misha here. Does the same thing in Ubuntu. I looked in .gimp but I
> couldn't find anything that looked like it set the theme colors. Then I
> went to gimp itself. Try opening gimp, pull down Edit menu, select
> Preferences, scroll down to Interface/Theme. Mine shows about 5 themes,
> defaulting to dark. I changed that to light, second from the bottom, and it
> seems like what I remember of old times. Of course click OK to exit, saving