diamonds on the soles of her shoes

There's a long list of things I never learned in life (formal etiquette, "no white after Labor Day", how to eat a lobster, how to say the alphabet backwards), and new rules that I was unaware of keep popping up. Sparked from a conversation I had with Helen, I now wonder if there's a formal rule about the color of the soles of your shoes.

Yes, really. Is there a Fashion Rule that dictates what color the sole of one's shoes should be, depending on the occasion?

Some background: I fell hard and fast for these satin pumps. You can see why, I'm sure.
I mean, look at them. Swoon.

Helen brought up a doubt as to their propriety, though. It's honestly something I've never thought about or heard of before, but that could very well be due only to ignorance on my part. Her thought is: the tan sole is a dealbreaker.


Not because there's anything wrong with tan, but because she was taught that tan soles are for daytime wear, while black soles (or Louboutin-red soles, for the extravagant) are for evening. The conjecture here is that wearing black stockings with tan-soled shoes looks awkward and undermines that whole "evening glamour" thing that you're going for with the fancy shoes.

Is this a thing? Have you heard of this? Am I a heathen for not knowing about this rule? Is there a "no nude soles for evening shoes" gospel?

I have a counter-point, however.
I think that if the sole-color debate is based on the assumption that one wears black stockings for evening, it's a false premise. I can think of very few situations in which I've worn black stockings (sheers, that is: opaque black tights are a daytime/all-the-time sort of legwear from December through February), and I'd argue that for formal occasions, few women bother to wear stockings at all. When we do, they're most often flesh-toned, and the contrast between stocking color and sole color is therefore a non-issue. The peep-toe option throws more confusion onto this, as peep-toes (more so with formal strappy shoes of all sorts) make wearing stockings awkward. (There are definitely ways to wear tights with peep-toes and look awesome, but I think all those ways are pretty much a daytime look or a casual thing.) I know you can get toe-less tights to expose one's toes in a peep-toe shoe, but that sort of defeats the purpose, I'd think. And strappy formal shoes: what then? Clearly, stockings aren't an option, so do strappy shoes get a pass on the sole-color rule?

Here, for comparison's sake, is a line-up of my more formal shoes. I can't think of many ways in which black satin pumps (center shoe) are daytime shoes, but the sole color remains resolutely beige. The black-soled contenders here are the tricolor satin peep-toes and the black patent peep-toes. Hmmm. The peep-toe component totally throws me for a loop.

What say you, fancy fashion people who know these sorts of things?