Raging Bull

I know all of you have seen it before, but I watched it for the first time completely. Excellent movie. The length of the movie was just right, leaving me wanting for more. I was wondering about one thing though. A montage scene was filmed in color. What was its purpose? Was it the only happy times in Jake's life? Any of you have an interpretation?
I have watched only 4 films of Scorcese - Raging Bull, Gangs of NY, Goodfellas and Aviator. I liked this the best. De Niro is amazing. The age of his wife, 15 - 20, is totally unbeleivable. She looked like 30 to me!