Type 1 in the Value data field if you want glassy, transparent bubbles, or type 0 for metallic bubbles.

Select Edit > New DWORD (32-bit) Value, and create a new DWORD called MaterialGlass. Go to HKEY_CURRENT_USER\Software\Microsoft\ To customize the Bubbles screensaver, launch the Registry Editor by typing regedit at the Start Search box or at a command prompt and pressing Enter. For the Ribbons screensaver, you can change the number and thickness of the ribbons.

For the Bubbles screensaver, for example, you can turn the bubbles metallic or keep them transparent, configure whether the bubbles should have shadows, and display the bubbles against the desktop or instead against a solid black background. If you're willing to get your hands dirty by using the Registry, though, you can customize both.

For reasons inexplicable to mere mortals, Microsoft doesn't allow you to customize how Windows Vista's screensavers work - for example, by changing how the bubbles look in the Bubbles screensaver, or the number or thickness of the ribbons in the Ribbons screensaver.