The decision to make all of the fantasy sequences black and white while the "real life" sequences are technicolor speaks so much to the unorthodox philosophy of this movie. The afterlife may not be such a bad place, but there's something more appealing, more romantic about the fleeting, the evanescent, the malleable. Eternity is static (everyone dead is wearing the uniform in which they died, clinging to the beliefs with which they died), while on earth there is love, sadness, hope, grief, learning, growing, drama, etc. The afterlife isn't necessarily heaven. Heaven is love, so choose life.
There's no way to approach this movie that doesn't find it an unmitigated success. It's wonderfully romantic. It's hilarious and entertaining. It's a fantasy spectacle with jaw dropping analog effects. It's a post-war curative that inspires patriotism and a spirit of cooperation. This is one of the best movies.