Black is no colour at all—it is the absence of colour

Back during your elementary school years, if your teacher asked you to mention the colours you know, you might probably mention, white, red, blue, black and on and on, but let me tell you this, maybe you might try modifying that knowledge you have in your head right now—black is no colour.
Okay to the "why" question. As humans, our ability to perceive an object's colour( let's say blue) is because the object absor0bs some light and reflects some light. The reflected light is the one you perceive to be the object's colour. You might be wondering, when you shine your torch or during a broad daylight(sunlight), light emitted from the light sources are single(white). A proof of this is in the image above, can you see the white light entering the prism from the left and thereafter on the other side can you see it split to different rainbow colours. The simple conclusion from this is that, the white beam of light from your torch or the sun is made up of the eight rainbow colours.
In essence, a blue ball appear blue because it absorbs all the other colours of the light spectrum while reflecting only the blue colour! If the ball does not, then it would not have a defined colour, you might then be perceiving the ball to have multiple colours at the same time.

Have you ever wondered why you can't see an object's colour in the dark? There is no light for the object to absorb and reflect—this is the simple answer. So when you take hold of a torchlight and fix it on the object, what happens? You perceive the object's colour—it absorbed some light and reflected the colour you perceive to be the object's colour.
So to the statement "black is colour at all", this is so because a black object absorbs all the light reflecting nothing. This is why you see black. For a white object—the direct opposite of black— it reflects all the light absorbing nothing.

Technological advantage of Black

You know, I have always wondered why scientist or technologist are always selective in terms of the materials they use for a particular innovation. The simple answer is that they consider the properties of each component before using them. To give an example, the feature of copper as a conductor makes it best for use in wires. There are other metals they could have picked but they choose copper, not because it is copper but because of its conducting properties.
The use of "Black" has been employed for use in solar panels. You might probably be indifference when selecting a particular type of solar panel, say blue or black. But after now, I think you should become a little selective when buying a solar panel. The reason is that black's property of total light absorption have made it a better solar panel compared to blue solar panels which makes for better efficiency in terms of higher output power—greater electricity generation.