ektachrome.
I shot my first roll of expired Kodak Ektachrome 64 a few years ago, and what I discovered, rather delightfully and unexpectedly after getting that first roll back from the lab, is that if you underexpose the film ever so slightly as the light starts to fade, your images will look like this: violet-blue, with bright whites popping out from the frame. Most lovely.
Update / Addendum: One more photo, from a different roll but around the same time of day:
At 64 speed, Ektachrome doesn’t give you much latitude, and will most certainly frustrate you if you’re trying to shoot indoors, but when you’re outside and the light is just-so — my goodness.