White and blue sunset

I was out and about one evening last week, when this scene happened on the western sky. I do think it is a sunset, it has to be. But I doubt I have ever seen white sunset. Orange, yes, sometimes red. At twilight, you typically do not see any sun at all anymore. And additionally, this evening, the clouds where just gorgeous.
I had my DSLR with me, quite accidentally, and a tripod. I was taking some photos at work earlier that day, I do not normally carry all those things around. I was so glad, as I could record this unusual scene!