Actually, I believe the sky is blue due to diffusion.

;-)

Light from the sun is scattered by earth's atmosphere. As it is scatterred, all the visible colors of the spectrum, except for blue and violet, are absorbed somewhat. This causes the sky to take on a violet/blue color. However, since the human eye cannot see higher frequencies of light, we simply see the sky as blue.

Why, thank you for the informative scientific lesson of the day!

You're all too cool!