The sky is blue. In most places, that sentence exemplifies a self-evident statement. Of course the sky is blue; what were you expecting, pink?
Well, yes. Here in Los Angeles, the sky is nearly as likely to be pink, or violet, or, depending on the sun's heat on the ocean or fires in the hills, opalescent white or gloomy, smoky gray. There's a red sky at night on enough evenings that sailor's delight must be a frequent occurrence in Santa Monica Bay. Sometimes, as the Traveling Wilburys once sang, "The sky ain't blue/ It's kinda yellow/ You know it's true." And of course, sometimes it's a filthy brown.
In a basin that so often fills with smog and haze, it is worth noting when it is possible, as it has been lately, (at least a few miles inland) to see the wild blue yonder.