What is the darker form produced by adding black to acrylic colour called?

Correct answer: Shade

The governing colour-theory concept is value modification. Adding black to a base colour creates a darker version called a shade, so option D is correct. A tint is made by adding white, while a tone is commonly made by adding grey or a neutral colour. A wash refers to a thin, diluted application of paint, not specifically a darkened colour mixture. The quantity of black determines how strongly the original colour is darkened.