The Menu bar in Leopard is transparent. Why Apple decided to do this, I don't know. I think it looks bad.

That does not look good.

You can convert the Menu bar to a solid white strip with Eternal Storms Software's OpaqueMenuBar, a free utility (donations accepted).

Download OpaqueMenuBar, move it to your Applications folder, and then double-click it. You'll soon see that your Menu bar is no longer transparent. Unfortunately, it doesn't apply to the pull-down menus.

That's better.

If you decide that you want to completely commit yourself to the Leopard experience and you want the transparent Menu bar back, here's how to revert the Menu bar back to its transparent self.

To disable OpaqueManuBar, you need to kill it in Activity Monitor.

1. Launch Activity Monitor (Applications > Utilities).
2. In the list of processes, look for OpaqueMenuBar. Click on it.
3. Click on the Quit Process button in the upper left.

The other way to stop OpaqueMenuBar is to launch the Terminal (Applications > Utilities), type killall OpaqueMenuBar and press Return.