When two rays of different colors, such as red and green, cross each other, the colors projected on the wall remain distinct as red and green. However, the human eye perceives the combination of these colors as yellow due to the way our color receptors (cones) are stimulated. This perception occurs because the eye cannot resolve the two colors when viewed from a distance, leading to a mixed signal interpreted by the brain. The phenomenon is further explained by the fact that yellow light stimulates both red and green receptors similarly, resulting in the same perception. Understanding this interaction highlights the biological basis of color vision and perception.