Fascinating! Listen to this podcast below discussing why we see colours in black & white movies.
Film colorization (or colourisation) is any process that adds color to black-and-white, sepia, or other monochrome moving-picture images. It may be done as a special effect, to modernize black-and-white films, or to restore color films. Examples date from the early 20th century, but colorization has become common with the advent of digital image processing.