This has been a subject for debate during a long time. And there is more than one way to look at this and the answer depends on weather you define colour as something generated by light or if you simply look at it as a colour.
Black is a colour that absorbs everything including light. A black object absorbs all colours and no colours are reflected back to the eye. So with that background I guess one can say that black isn’t a colour.
Some says that black is the absence of colour but if you combine the three colours red, yellow and blue you wont get an absolutely black colour but the result will be very close to black, so a mix of three colours should be regarded as a colour, don’t you think?
So I conclude the following about black: a black object absorbs all colours and no colours are reflected back to the eye. If colour is seen as something generated by light black can be defined as no light.
Black is the mix of several colours and can therefor be regarded as a colour.
So, now lets move on with more about this exiting colour!