Put some #C010UR back-a-round!
I’ve noticed recently a lot of apps in the Windows 8 Store have the default grey as their background/accent colours. It’s been annoying me looking at the Store and just seeing loads of grey. The colour helps differentiate your app from others and makes the app detail page look much more interesting. The only reason to have the default grey is if you don’t know how to change it or you actually think it is the right look for your app (hah). This is why I’m showing you the solution to the former:
Open your Visual Studio solution. In the ‘Package.appxmanifest’ file look for the Visual Assets page and here is ‘Background color’. Choose a hex value that suits your app. This value is also the background colour of transparent logos, the colour of the app tile in the Start menu teaser when you hover over the left corner of the screen, and the colour of the background in semantic view on the Start menu. I hope this helps get some diversity into the Store.