In the production design, the color blue was used to represent love. Red, the traditional color of love, is only seen in one shot of the film, which is in the form of an origami bird on Summer’s tree in her apartment. (It also appears in the final scene as a red blouse on Minka Kelly, but the commentators do not mention this.)
Read more at Film School Rejects: http://filmschoolrejects.com/features/24-things-we-learned-from-the-500-days-of-summer-commentary.php#ixzz3oMQxf9gS
Read more at http://filmschoolrejects.com/features/24-things-we-learned-from-the-500-days-of-summer-commentary.php#yu57dTpY5y6y7opY.99