Microsoft includes three default "shell styles" with the Windows XP Luna theme: Homestead, Metallic, and NormalColor.

You can see these three styles in the "Welcome to Windows" and "Log On to Windows" screens during logon.

To change the style, open regedit and go to: HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\ThemeManager
Change the "ColorName" key value to either "Homestead" or "Metallic". "Homestead" will show the title bars in an olive color. "Metallic" will show them in a silver color.

Log off or reboot to see the change.

Note: this will only work on the original Ctrl+Alt+Del log on screen, not the new Welcome screen.