Light has a colour an object has not, an object merely has the ability to absorb, reflect or emit light. A banana in the dark "is" not yellow.Colour contains light. E.g. in Haskell it could be encoded like this (simplified, there are actually many more kinds of light):
data Colour = Colour Red Green Blue
data Red = Red Int
data Green = Green Int
data Blue = Blue Int
So Red, Green, and Blue are kinds of light. And colour contains all those lights. So when you see a light you really see a colour that contains the light. Just like how when you see my writing you really see a screen that contains my writing (or maybe paper if you printed my post out to put it in a frame and hang it above your door or perhas even gold that contains my writing if you edged my writings into gold where they belong). Colour is that which contains light. Ever heard that light is waves yet can travel through a vacuum even though waves always need a medium to travel? That is because colour is the medium of light. Light waves travel through colour.
Colour is also a monoid and black is the identity because black has all values on 0 and if you add black to any colour X then the result will be the colour X. If black is not a colour, then colours do not form a monoid. That is why black must be a colour. Would you take 0 out of the numbers and then lose the monoid with the + operator? Of course not. You would need to be a total barbaric fool to do that. Likewise you would never take black out of the colours because if you did take black out of the colours then that would demote the colours from their status as proper monoid.