How can I switch themes in Visual Studio 2012

In Visual Studio 2012, open the Options dialog (Tools -> Options). Under Environment -> General, the first setting is "Color theme." You can use this to switch between Light and Dark.

The shell theme is distinct from the editor theme--you can use any editor fonts and colors settings with either shell theme.

There is also a Color Theme Editor extension that can be used to create new themes.

Tools -> Options ->Environment -> General

Or use new Quick Launch to open Options

For more themes, download Microsoft Visual Studio 2012 Color Theme Editor for more themes including good old VS2010 theme.

Look at this video for a demo.