Sometimes we watch and wait, and the sky simply fades from blue to gray to black. So what's up with the sky colors?
The secret can be found in the earth's atmosphere. Light is made up of waves that interact as they travel through this atmospheric soup.
This soup, or atmosphere includes gas molecules in a mixture of 78% nitrogen, 21% oxygen argon gas and water vapor, droplets or ice crystals. Small solid particles such as dust, ashes, pollen, soot, and in the case of California's beaches salt from the oceans.
The weather comes into play as one major component in affecting the color of the sky.
As the sun begins to set, light travels farther through the atmosphere before it reaches you and your vision. The longer the distance, the more light it is scattered and reflected.
As less reaches you directly, the sun appears less bright. The color of the sun itself appears to change, first to orange and then to red. This is because even more of the short wavelength blues and greens are now scattered. Only longer wavelengths are left in the direct beam that reaches your eyes. The sky around the setting sun may take on many colors. The most spectacular shows occur when the air contains many small particles of dust or water.
These particles reflect light in all directions. Then, as some of the light heads towards you, different amounts of the shorter wavelength colors are scattered out. You see the longer wavelengths, and the sky appears red, pink or orange.
Why is the sun yellow or white? On Earth, the sun appears yellow. If you were out in space, or on the moon, the sun would look white. In space, there is no atmosphere to scatter the sun's light. On Earth, some of the shorter wavelength light (the blues and violets) are removed from the direct rays of the sun by scattering. The remaining colors together appear yellow. Because there is no atmosphere out in space and no scattered light to reach your eyes, the sky looks dark and black, instead of blue.