It's tough to say for sure, but according to IMDB.com its format is "color (Technicolor)" (not sure what that says about original format). Also my dad says he is pretty sure that it was in color when he saw it in theaters. As a matter of fact, all of the clips and trailers I can find show it in color. Did you ever see it in black and white?
I saw it in the theater when I was about 12 years old. It ALWAYS has been in color! For one thing, colorization is a relatively recent thing. Before that, they had to hand-color frames if they needed color.