Final answer:
The Young-Helmholtz theory of color vision states that there are three primary colors, which correspond to the three types of cones. Combinations of these primary colors can produce all the hues that we can distinguish.
Step-by-step explanation:
The Young-Helmholtz theory of color vision states that there are three primary colors, which correspond to the three types of cones in our eyes. These cones are responsible for our ability to perceive different colors. The theory proposes that combinations of these primary colors can produce all the hues that we can distinguish.