Why is Lan Yu purple?

Caused by the scattering and refraction of solar light. When the weather is gloomy and humid, the moisture in the atmosphere will lead to the scattering and refraction of the sun's light, so that the blue wavelength in the light will be scattered more, while the red and purple wavelengths will pass through the atmosphere more easily, and the sky will appear purple. This phenomenon is called magnificent purple, which mainly appears in rainy weather.