Are black and white colors?

I think you might get either a yes or no answer on this, depending on what someone is thinking about when answering the question.

If you are a printer with different colored inks, then black ink would be one of them. And of the different papers you might choose, one would be white.
But I would say no, they are not colors. Something white, like snow or white paper, is white because it reflects light of all colors equally. And something black, like coal, is black because it absorbs light of all colors equally. Something that is colored, like a rose, will be red if it reflects red light and absorbs light of other colors.

You can see why I think the answer is no. But I would not like to argue about this question with a printer.