Why would you add black paint to a color?

To make it darker. Shades of grey (including black and white) also can desaturate colours (make them less bright).Why would you add black paint to a color?
Be careful when adding black to a colour in order to make it darker. It may turn out muddy. Usually black mixed with yellow makes a sort of dingy green. This can be useful if that is the look you are going for, but otherwise, try darkening with a complementary colour or some other darker colour, like adding purple to red etc. or adding blue or brown rather than straight black.Why would you add black paint to a color?
I add it to yellow ocher to make a medium olive green. If you do that, though, make sure you are using ivory black. Black is considered another blue.
To make it darker? Just a little bit.
To dull it down.

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