Change the workspace theme
Blend for Visual Studio 2012 comes with two themes for the workspace: Dark and Light. Changing your workspace theme does not affect the appearance of your project.
The themes of the Blend for Visual Studio workspace: dark (left) and light (right)
To change your workspace theme
On the Tools menu, click Options.
In the Options dialog box, select Workspace (on the left).
Next to Theme, select either Dark or Light. The theme changes immediately so that you can preview it.
Click OK.