JFrame background is white on Mac, grey on PC

I have a program which uses a JFrame set to be in full-screen mode, using

DisplayMode oldMode = device.getDisplayMode();

this.setSize(new Dimension(oldMode.getWidth(), oldMode.getHeight()));

this.validate();

this.setUndecorated(true);

this.setBackground(Color.white);

this.setForeground(Color.white);

device.setFullScreenWindow(this);

I set the background to be white here, and in several other places in the code (e.g. just before a repaint() comand). However, while the background is white on the Mac I have been programming this on, it is always an ugly grey on PCs.

The various JPanels in the JFrame, all of which are set to have white backgrounds and be opaque, do indeed have white backgrounds. They just hang there as white rectangles on a grey background.

How can I get my JFrame's background to be white?

Thanks!

[995 byte] By [Asbestosa] at [2007-10-3 6:24:53]