This fascinating article, which is inspired by what the writer found to be a fascinating podcast (linked inside the article), posits that in ancient times there was no such thing as the colour blue.
Although the atmosphere overhead has always existed in the same format as we know it, there was no collective definition of the colour therefore nobody technically could perceive that the sky was/is blue. (At least not in a way that allowed them to differentiate it substantively from other colours)
We've always been intrigued by the way in which human perception is moulded by our ability- or propensity- to describe an experience, and this is a classic example. Did the ancients never marvel at the exquisite tones of a Mediterranian azure (Well, according to the piece they compared it to wine!), or attempt to describe the hues of a glacial crevice? (This must have fallen into one of the ways they described icy white).
Let's not split (fashionably blue) hairs on whether reality is in the describing; since we can now appreciate it let's just take a moment to appreciate a few recent blue Toronto moments!