What is the main change when black is added to a primary colour?

Correct answer: The value becomes darker

The governing concept is colour value. When black is mixed into a primary colour, the colour becomes darker and forms a shade. For example, adding black to red produces a darker red, although the exact appearance depends on the amount and pigment. It does not automatically become a secondary colour, because secondary colours result from mixing two primary colours. Black also does not necessarily change temperature or erase the colour’s identity.