There are a number of resources that can be found via Google (i.e. "app design") but Smashing Magazine has some good articles relating to app design and layout in general. You can also try searching for "beautiful apps" which brings up links to collections of different apps that might provide an idea. As far as color goes, I like searching for web site templates or 'best web design of 2011' collections and finding a color scheme that I like or think would work well with the general feel of what my product does. Remember, "Imitation is the sincerest form of flattery"