I don't know what kind of set this would go in, but I'm intrigued by it. It's the probably the closest interaction of two colors, probably closer that hybrid. See also Destiny Blade.

What do you mean by "it's the closest interaction of two colours"? As far as I can tell, the colour pie per se wouldn't have any problem with, say, an instant for with "~ is black. Destroy target artifact or enchantment." How "close" you make the effect to another colour that could have it depends entirely on the effect.

You need to be careful though. For one thing, players look at the frames of their cards to decide what to play in what decks. This card would get a collector number among the white cards, and I can imagine a number of players putting it in a deck with Plains, trying to cast it and being startled when their opponent says they can't.

(Well, okay, not this one, because it's an extremely niche effect. I think it's managed to be worse than Kumano's Blessing, which takes some doing. But Destiny Blade is extremely playable.)

The other reason to be careful with this effect is because it doesn't actually do much. Ghostfire was a sensible thing to do with it, because protection from red often interferes with a burn deck's attempts to burn creatures. But because this card doesn't target, there are very few cards which would care that this is white; Angel's Feather and friends are the only kind of thing.

That said, I have been trying to come up with a place to put Black and White and Red All Over for several months, just because I love what Multiverse does to the pinlines :)

I mean that I tried my best to find an effect that white could do while using red mana or black mana, rather than trying to exactly find an intersection between the colors as hybrid does. This is more of a thought experiment than something I would actually put in a set.