What problem may occur if too much black is mixed into a colour?

Correct answer: The original colour may lose brightness and identity

The governing concept is control of colour value and saturation when making a shade. Too much black makes the mixture darker, but it can also dull the brightness and obscure the identity of the original hue, producing a muddy-looking result. It does not automatically make paint transparent or warm, and it cannot change the smoothness of the paper. Black should be added gradually.