Blue is a favored color of many humans. While blue skies and oceans are a common visual experience, this color is less frequently observed in flowers. We first review how blue has been important in human culture, and thus how our perception of blue has likely influenced the way of scientifically evaluating signals produced in nature, including approaches as disparate as Goethe’s Farbenlehre, Linneaus’ plant taxonomy, and current studies of plant-pollinator networks. We discuss the fact that most animals, however, have different vision to humans; for example, bee pollinators have trichromatic vision based on UV-, Blue-, and Green-sensitive photoreceptors with innate preferences for predominantly short-wavelength reflecting colors, including what we perceive as blue. The subsequent evolution of blue flowers may be driven by increased competition for pollinators, both because of a harsher environment (as at high altitude) or from high diversity and density of flowering plants (as in nutrient-rich meadows). The adaptive value of blue flowers should also be reinforced by nutrient richness or other factors, abiotic and biotic, that may reduce extra costs of blue-pigments synthesis. We thus provide new perspectives emphasizing that, while humans view blue as a less frequently evolved color in nature, to understand signaling, it is essential to employ models of biologically relevant observers. By doing so, we conclude that short wavelength reflecting blue flowers are indeed frequent in nature when considering the color vision and preferences of bees.

蓝色是许多人喜欢的颜色。虽然蓝天和海洋是一种常见的视觉体验，但在花朵中很少观察到这种颜色。我们首先回顾蓝色在人类文化中的重要性，以及我们对蓝色的看法如何影响科学评估自然界产生的信号的方式，包括歌德的法本勒、林诺的植物分类学和当前的植物研究等不同的方法-传粉媒介网络。然而，我们讨论了这样一个事实：大多数动物的视力与人类不同。例如，蜜蜂传粉者具有基于紫外线、蓝色和绿色敏感感光器的三色视觉，其天生偏好主要是短波长反射的颜色，包括我们认为的蓝色。蓝色花随后的进化可能是由于对授粉媒介的竞争加剧所驱动的，这既是由于更恶劣的环境（如在高海拔地区），也是由于开花植物的高多样性和密度（如在营养丰富的草地中）。蓝色花的适应价值还应该通过营养丰富度或其他非生物和生物因素来增强，这可能会减少蓝色颜料合成的额外成本。因此，我们提供了新的观点，强调虽然人类将蓝色视为自然界中不太频繁进化的颜色，但为了理解信号传导，必须采用生物学相关观察者的模型。通过这样做，我们得出结论，考虑到蜜蜂的色觉和偏好，短波长反射蓝色花朵在自然界中确实很常见。