Final answer:
The three colors that form an equilateral triangle on a color wheel are the primary colors: red, yellow, and blue.
Step-by-step explanation:
The combination of three colors forming an equilateral triangle on a color wheel are the primary colors, which are red, yellow, and blue. These colors are positioned equidistant from each other on the color wheel, representing the foundation from which all other colors are derived. Secondary colors such as orange, green, and violet are created by mixing pairs of primary colors. Tertiary colors are a result of mixing a primary color with an adjacent secondary color, leading to various hues such as red-orange or yellow-green.