Well the thing is that colour is usually a representation of the primaries, blue, yellow and red. Black and white are unnatural 'colours' which is why most artists don't use either, and often to represent black or a dark area using a very dark blue, dark purple etc. Which is why often people refer to black and white as shades not colours.
In pixel art it is common to have a highlight area around the pixel art which is represented by black. So you can see the problem if the definition of colour isn't specific in this case. I think science isn't a helpful tool in this situation because we don't live in a reality of pure absence of light. We always have a degree of light.