Primary colors are those colors which cannot be produced by mixing other colors (Option D). They are fundamental in both light and pigment contexts. In the additive color model, used for light, the primary colors are red, green, and blue. These colors combine in various ways to produce other colors, including white light when combined in equal intensities. For example, red and green light mix to produce yellow, green and blue produce cyan, and blue and red produce magenta. In the subtractive color model, used for pigments and dyes, the primary colors are red, yellow, and blue. These colors mix to create other hues, with red and yellow producing orange, yellow and blue producing green, and blue and red producing purple. Understanding primary colors is essential in fields such as art, design, and color science, as they form the foundation for color mixing and the creation of a full spectrum of colors.