Windows/Visual Styles/Watercolor

Watercolor is the name of a placeholder theme created by Microsoft during development of the Windows XP operating system. It debuted in build 2250 and the last known build to include it was build 2419.

It was first introduced in build 2250, being called "Professional", and was not enabled by default. However, an earlier version of the theme is present in build 2223, though it is broken and unstable.