You might be running into this (from the Qt Style Sheets Reference):
So try setting the border as well.QPushButton
Supports the box model. Supports the :default, :flat, :checked pseudo states.
For QPushButton with a menu, the menu indicator is styled using the ::menu-indicator subcontrol. Appearance of checkable push buttons can be customized using the : open and : closed pseudo-states.
Warning: If you only set a background-color on a QPushButton, the background may not appear unless you set the border property to some value. This is because, by default, the QPushButton draws a native border which completely overlaps the background-color. For example,
QPushButton { background-color: red; border: none; }
See Customizing QPushButton for an example.
Bookmarks