Changing button color doesn't work !

[fres]

When I change the color of the Button "OK", it doesn't work

This is what happen:

I don't even see the button "OK", so I want to change the button color in white, but it doesn't work when i write this :
msgBox.setStyleSheet("background : solid black; QMessageBox QPushButton{color: white; }");

[nagesh]

@fres try setting like this
msgBox.setStyleSheet("QDialog{background-color:black;}QPushButton{background-color:white;}");

[fres]

Thanks it works!