B/W, or colourized?..

When I was a kid, growing up in Brussels, I had the 'book of the film', which consisted of stills from the movie, with a written narrative. All the pictures were in black and white, except for the last, which showed the boy flying away with all of the balloons, one of which was coloured red.

It seems odd that they would print a book in B/W, using stills from a coloured film, so my question is this: was this originally a B/W film that has since been 'colourized', and if so, can I buy a copy of the original monochrome version?..

I've seen things you people wouldn't believe...