Simply swipe left on the Start screen to access
the App List, and then tap the Settings icon, as shown here.
Changing the Device Theme
Although most Windows Phone 8 devices use red
as the primary color for Live Tiles and some configuration options, you
can alter the device’s primary color by changing the device’s theme. Go
to the Settings screen and follow these steps:
1. Tap Theme.
2. Set the background to either Dark or Light.
3. Choose an Accent color.