What does running
Code:
calibre-debug -c "from PyQt4.Qt import QApplication, QPalette; app = QApplication([]); print unicode(QApplication.palette().color(QPalette.Normal, QPalette.Window).name()); print unicode(QApplication.palette().color(QPalette.Normal, QPalette.WindowText).name());"
in terminal.app give you
(you may need to install the calibre command line tools first via preferences->miscellaneous)