HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0\General\CurrentTheme\
Contains a guid (in the case of dark 1ded0138-47ce-435e-84ef-9ec1f439b749
This guid maps to a list of keys under
HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0_Config\Themes\
1ded0138-47ce-435e-84ef-9ec1f439b749 = Dark
a5c004b4-2d4b-494e-bf01-45fc492522c7 = High Contrast
de3dbbcd-f642-433c-8353-8f1df4370aba = Light