One of the best examples of the technique I have ever seen was a portrait of Sigourney Weaver, done by Robert Mapplethorpe. (Yes, the bullwhip guy.) Let's see if I can find it.
Nope. can't ... bummer. It was (is?) astonishingly beautiful.
In any case, when we literally remove all colour from the image, we need the model to put all sorts of figurative colour into the image with body-language and facial expression. In this image, not only is it literally colourless it's figuratively colourless as well.
Very interesting observations. I hadn’t even noticed the pictures were shot in color!