In this app, the user can record his mood conveniently and choose a kind of color to mark the mood, then he can re-ceive another person's diary who chooses the same color as his. "Blue" hopes that people liveing in blundering and roaring cities can achieve their self-examination and obser-vations on others in the way of writing diaries. There is only one kind of color and we use the simpliest way to memorize our mood.

Painting is his way to record his life and observe others' life. A person's life experience may become another's obser-vation. I extract some characters in paintings of Picasso's Blue Period to explore subtle and accidental associativity of emotion between different people.