Sometime ago my mother told me she went to see this movie in the theater which was showing old films.. It's call Ballon Rouge. It's a french film made in 1956 directed by Albert Lamorisse.
This film is very beautiful. Contrast of monotone city scape of Paris and the Red balloon is wonderful. I haven't seen entire film so I hope to see it one day soon..
Meanwhile, I found this trailer on YouTube so take a look!