The primary colors in color theory are red, blue, and yellow. These hues are considered fundamental because they cannot be created by mixing other colors. In both the traditional color wheel (RYB) and the RGB model used in digital screens, these colors serve as the building blocks for a wide range of other colors. By mixing primary colors together, secondary colors like green, orange, and purple are produced. Understanding primary colors is essential for artists, designers, and anyone working with color, as it provides a foundation for creating visually appealing combinations.