Luna

Luna is the visual style that shipped with Windows XP and some betas of Whistler (from 2428 onwards). It was also available in all Longhorn builds before reset (although from 4042 onwards, the taskbar and sidebar would still display in Longhorn style). Notably in 3683, the Windows logo on the Luna 'start button' is all white rather than coloured as it was in Windows XP. Notably it is known as 'Windows XP theme' in the Control Panel.

Luna in Windows XP (build 2481 onwards) had three colour schemes: Luna Blue (the default), Luna Silver and Luna Olive Green. While Royale, Royale Noir, Zune and Embedded are often considered separate themes, they are technically subsets of Luna. This video shows all the Windows XP themes.