So I'm reading the Hobbit and it describes Smaug as being red. Then I read the ROTK appendix and it called him Smaug the Golden. And in the movie, I think he looks black.
I keep forgetting to mention one of my favorite new parts in the movie, showing the dwarves hanging on ropes in a crack in the earth, mining gems. I've never actually seen a visual representation of what they do before and that was really cool.