Comment by donrhummy

That's not how flat ui design works. You can make single-color boxes and it won't look modern. Flat UI is about beautiful color palettes that are well matched and which convey the proper information without over embellishing. A few good examples:

http://inspirationhut.net/wp-content/uploads/2013/08/23.png http://maxcdn.webappers.com/img/2013/03/flat-ui.png