Final answer:
In art, '0' usually refers to the original color before changing its value by adding black to create a shade or white for a tint. The value of a color is used by artists for shading or highlighting, giving depth to the painting.
Step-by-step explanation:
In the context of painting or color theory, the '0' often refers to the original hue before the addition of black or white to create different shades. The value of a color is an essential aspect that determines its overall lightness or darkness. By mixing a color with black, an artist can create a shade, which is a darker version of the original hue. Alternatively, mixing with white produces a tint, which is a lighter version. This technique provides artists with an array of gradations of one color that they can use for shading or highlighting in a painting. This helps to give depth and dimension to their work.