Some backgrounds look best with Mac OS X’s menu bar transparent, while others look terrible. I suppose this is why Apple allows you to toggle the transparency of the menu bar in the Desktop & Screensaver preference pane in System Preferences (as seen in the image above).

The ability to disable the transparency of the original translucent menu bar came in the 10.5.2 update released by Apple, since then users have had the ability to toggle the setting. What this comes down to is individual preference, I encourage you to try your menu bar both with and without transparency enabled to find what suits you best. Although this may be a well known feature for long-time mac users (or just Leopard early adopters), tips like this help newcomers to the mac feel at home, look for more tips like this one in our Mac Basics category.