[Unit 00]

Are you referring to the window color in mabinogi, or the window color for Microsoft's Windows.

To change the color in Mabinogi you hit the window key on you keyboard (or click the the icon while ingame where the start menu woul be located) and click on options. I do not remember where it is in the window that pops up, but I believe the default is sky blue.

Changing the window color in Microsoft Windows depens on what OS you are running. (The method is essentially the same, but Vista will open a more standard window while xp will open something more like a properties window)