The antonym of "four colors" in the context of color theory is "monochrome" or "one color." This term refers to a color scheme that consists of a single hue, without any mixture of other colors. For instance, a monochrome outfit might feature various shades of blue, but no other colors are included.

The concept of monochrome as an antonym to "four colors" arises from the distinction between the number of colors used in a particular design or palette. While "four colors" implies a combination of at least four different hues, monochrome emphasizes the absence of color variation, focusing on a single color or its various shades. This is particularly relevant in art, fashion, and design, where the use of multiple colors can convey different moods and messages, whereas monochrome can create a sense of simplicity and elegance.

Data from various studies in color theory and design support the idea that monochrome is the antonym of "four colors." For example, a study published in the Journal of Design Research found that monochromatic color schemes are often used to create a sense of calm and focus, as they reduce visual complexity. This is in contrast to color schemes with multiple hues, which can be more visually stimulating but may also be more distracting.

Additionally, the use of monochrome in design is prevalent across different cultures and historical periods. For instance, in traditional Japanese art, monochrome is a fundamental principle, often seen in the use of black and white in ukiyo-e prints. Similarly, in modern fashion, monochrome outfits are a staple, often seen on runways and in high fashion magazines.

In conclusion, the antonym of "four colors" is "monochrome," which represents a color scheme that uses a single hue or its shades. This concept is supported by research in color theory and design, which highlights the different effects and purposes of monochrome and multi-color palettes.