Sky color depends widely on time of day AND time of year. For instance, there's a saying here in my area of the states: "October's bright blue weather". That's because of the angle of the sun in the sky during that time of year, the dryness of the air (moisture, smog, etc all affect the color as well). There really is no one standard color. It depends on where you are, what time of day it is, what time of year it is and the weather conditions.

Laurie