Unless you are developing a "native app" (which these days needs some justification) - the idea of designing for a particular color or frame to the device seems like a fool's errand. Phones come ottb in many colors and shapes, tablets, etc.... all have some flavor of color twist to set the hardware apart - and just when you might have thought you considered all of that and provisioned your application (somehow) for that?
Cases / wrappers / stands come into play.
Your time is better spent focusing on how to present information "within the device view-pane" rather than how that view might look against a periwinkle rubber bumper someone has wrapped it in.
Thats not to say you shouldn't consider device nuisances, interface, tactile appreciation, etc.. that you should design for.