What does the term "color wheel" primarily categorize?

The term "color wheel" primarily categorizes color relationships. The color wheel visually represents how different colors relate to one another, showcasing primary, secondary, and tertiary colors. This tool helps in understanding color harmony, including concepts such as complementary, analogous, and triadic color schemes.

By utilizing a color wheel, nail technicians and artists can easily identify combinations that produce desired aesthetic effects, whether in nail design, makeup, or other artistic endeavors. This is critical for creating visually appealing arrangements and understanding how to balance colors effectively.

In contrast, the other options address aspects of color theory but do not define the primary function of the color wheel itself. For instance, colors based on light spectrum relate more to physics and optics, shades of black and white focus solely on grayscale, and monochromatic colors refer specifically to variations within a single hue, none of which encapsulate the broader concept of color relationships as effectively as the correct choice does.