[Ardour-Users] Ardour buttons unreadable on openSUSE Leap

[Brbney]

When I first run Ardour I see
Welcome to Ardour... a few things that need to be configured before you 
start using the program.

The buttons lower right are pure white rectangles. How can I make them 
legible?

I've tried various alternate "Application Color Scheme" settings under 
System Settings but they have no affect at all. I'm running KDE desktop 
environment with Plasma 5 desktop.

I found some color definitions in /etc/ardour4/dark.colors but I have no 
idea which are relevant here, if any.
Any clues?