My teacher arranged for all the students taking German to watch it in the school's massive auditorium (bigger than any theater I've been in).
Then we were tested on it.
Jimbo,
Do you understand the concept of symbolism?
That movie is filled from top to bottom with symbolism.
Now, I must be honest and say I do not remember how I answered on the test I took, that was a long time ago, but if I had to guess, based on what I remember of the movie, the use of B&W was to show the polarizing effect on Europe created by the Nazi regime. The little girl in red was a symbol of hope for the future, that the polarization could be undone.
If someone colorized this movie, it would remove that symbolism. It would destroy the full intent of the film. Unlike the Florida voter of 2000, Steven Spielberg's intent is not up for debate. He knew precisely what he was doing, and why.