Is black a colour or a shade?

It's not a shade. Shades are different intensities of colours that can vary, and you can't have pale black or dark white.

Whether black is a colour or not is debatable and depends on where you are coming from. In scientific terms, black and white are not colours. White is a mix of all colours and black is the absence of all colours in terms of light mixing. Colours in this context are different wavelengths of light that stimulate our eyes in different ways.

On the other hand, if you are coming from the direction of paintpots, then black and white are colours. Here, colours are the different things you splodge on a surface, and you don't have colourless paint.

Basically, the issue comes down to being a scientist or an ordinary person. The scientific terms are correct in scientific contexts. The ordinary terms are correct in ordinary contexts.

color
https://en.wikipedia.org/wiki/Black

As Baloo and Krammar's own site have indicated, black represents the absence of color. As for whether it can be called a color in painting, it is generally used to indicate such absence -- where the light doesn't fall, where color cannot be reflected back.

Black is neither.

To use the first words of Krammars posting.......

"Black while commonly referred to as a color, is in actuality the abscence of color and as a word has several subtle differences in meaning."

Black is Black. Nothing more.