Which colors are known as secondary colors?

Secondary colors are defined as colors that are created by mixing equal parts of two primary colors. In color theory, the primary colors are red, blue, and yellow. When these colors are mixed together in pairs, the result is orange (red + yellow), green (blue + yellow), and violet (blue + red). This principle is foundational in both art and design, as understanding color mixing helps in achieving the desired aesthetics in various applications, especially in hair coloring.

The other options do not accurately describe secondary colors. For instance, colors that cannot be mixed would refer to colors that are inherently distinct and do not stem from blending primary hues, which does not apply to secondary colors. The idea of colors being darker or lighter also does not pertain to the definition of secondary colors, as this classification is solely based on the mixing process rather than the properties of lightness or darkness.