The color of the sky appears blue, rather than green, due to a phenomenon called Rayleigh scattering. Rayleigh scattering is the scattering of light particles (photons) by molecules and tiny particles in the Earth's atmosphere. It is responsible for the color of the sky during the daytime.
The Sun emits light across a broad spectrum of colors, including all the colors of the rainbow. However, shorter-wavelength light, such as blue and violet, is scattered more easily by the molecules in the atmosphere compared to longer-wavelength light, such as red and green.
When sunlight reaches the Earth's atmosphere, the blue and violet light is scattered in all directions by the nitrogen and oxygen molecules in the air. This scattered blue light is then redirected and reaches our eyes from all directions, creating the effect of a blue sky.
On the other hand, the green light, which has a slightly longer wavelength, is scattered less compared to blue light. Therefore, the predominant color we perceive in the sky is blue rather than green.
Additionally, human eyes are more sensitive to blue light than green light, which can also contribute to our perception of a predominantly blue sky.
It's important to note that the color of the sky can vary under different atmospheric conditions, such as during sunrise or sunset when the light passes through a larger portion of the atmosphere, leading to scattering of longer-wavelength colors like red and orange, resulting in colorful skies.