SKY IS BLUE BUT WHY ?

WHY THE SKY IS BLUE ?

The molecules that exist in the earth's atmosphere are efficient in scattering the light, profoundly the blue light than that of red (sunlight) due to the red color having a greater wavelength.
So, some blue light gets scattered out of the direct sunbeam and goes into the rest of the sky.

THEN WHY DO THE SUNSETS ARE RED?

Sunsets on Earth have a red, orange, or golden color because the sunlight passes through so much atmosphere as it comes over the horizon that all the blue light gets scattered away.