The background color of e.g. the stage selection buttons in the middle have a grey background instead of a blue one. This behavior is not inclusive for ToggleButtons, but can also be seen if I press down and hold a normal Button.

Occurs in unstable as well as in OR 15.03.

The issue is not present in buttons of a JOptionPane:

[macOS Monterey 12.1, MacBook Pro M1]