Why do bee-pollinated orchids usually avoid red flower colors?

Bee-pollinated orchids generally avoid red flower colors because bees are unable to perceive red as a distinct color. Instead, bees perceive red wavelengths as black or gray, making such flowers less effective as visual "advertisements" for pollinators.1

In contrast, bees possess a trichromatic color vision system with peak sensitivities in the ultraviolet, blue, and green regions of the spectrum. Consequently, flowers that rely on bee pollination typically feature bright colors—such as yellow, blue, and ultraviolet—that evoke a strong response in the bee’s eye. These colors, often accompanied by nectar guides, serve as essential signals to orient bees toward the flower's center for successful pollination.213