If you'd like to change the VS 2012 IDE's Environment Theme then you need to click the Tools Menu and choose Options: Then a new Dialog Window will appear. There inside General->Environment you can set the theme of the VS 2012 IDE. Personally, I don't like the Dark Theme, but it's up to you ;)
Windows Store Development Tips and Tricks -3 : Device Settings
Windows Store Development Tips and Tricks 4 : Taking ScreenShots in Simulator
Thank you guys
Nice tips and tricks!