Why do many bee-pollinated flowers have blue or yellow colors?

Many bee-pollinated flowers, or melittophilous flowers, exhibit yellow or blue colors because these hues, often combined with ultraviolet radiation, are highly visible and attractive to bees.123

Bees possess a trichromatic colour vision system with photoreceptors sensitive to ultraviolet, blue, and green wavelengths, but they are blind to red light. Consequently, flowers that appear yellow or blue to humans often feature specific patterns—such as nectar guides—that reflect ultraviolet light. These patterns act as visual signals that direct bees toward the flower's nectar source, ensuring efficient pollination.14526

Because bees and flowering plants coevolved, these colors and intricate patterns serve as effective "advertisements" that evoke a strong response in the bee’s compound eye, helping the insect locate food while facilitating the plant's reproductive success.236