Attraction The plant must first attract the vector. This is usually the function of the perianth. The attraction cues might be visual or olfactory. Visual cues Showy petals or sepals with obvious shape, size, and color for the vector's vision are important. Butterflies and birds are attracted to red and yellow colors, and the stark contrast between a dark red and a bright yellow is important.
Bees have vision that is shifted toward the blue end of our visible spectrum.
They do not see red colors but do see into the near-ultraviolet. Typically the red itself is attractive to other potential pollinators, but there is likely some other color pattern that works for the bee. It may be a pattern in the UV that we cannot see which actually attracts the bee. Moths and bats fly at night and the limited vision possibilities mean that a white or very pale color is more observable. Bull's eyes, splotches, and nectar guides are color patterns that form a high-contrast exhibit to make the flowers stand out against a background of green foliage.