[chopper]

Not so easy.

Folks see colors differently. That's why you can go into an electronics shop where someone has tuned all of the TVs to look the same. They will all look the same to him but not to others, who will say that there are color variations between sets. (I worked in a television/appliance shop in an earlier life).

However, your question implies that the sky is a constant color, with the distinction being which constant color, and there is the misdirection.

It's like the question "what color is a polar bear", hence the requirement for a usable definition.