In color theory, hue is one of the main properties of a color, defined technically as "the degree to which a stimulus can be described as similar to or different from stimuli that are described as red, orange, yellow, green...". Hue can be represented quantitatively by a single number, often corresponding to an angular position around a central or neutral point or axis on a color space coordinate diagram or color wheel, or by its dominant wavelength or by that of its complementary color. The other color appearance parameters are colorfulness, saturation (also known as intensity or chroma), lightness, and brightness.

When artists talk about hue, they are describing either pure color (no white, black, gray, or another color mixed with it) or the dominant pure color in the color that is being discussed. The hues are the primary colors - red, yellow, and blue - and the secondary colors - green, purple (called violet or magenta sometimes), and orange.

In everyday language, hue can also refer to the overall character or appearance of something, such as the hues of blue and green used to decorate a room.