At a friend's funeral a few years ago there was a young woman -- granddaughter? grandniece? -- who wore a very short, very tight one-shoulder black dress. It could have been that she was thinking "must wear black, and this is the only black thing I own," or "must dress up, and this is the only dressy thing I own." The widow, who wore a gray suit with a colorful purple print blouse, didn't care. She was just pleased to see everyone who came. I don't even remember what I wore to that funeral -- only that I was warmly welcomed by the widow and grown children.
Wakes/calling hours tend to be a lot less formal than funerals. Most people stop by after work and are wearing their work clothes. The loved ones don't even look twice at what they're wearing -- they are just happy to see them, whether they're in business suits or business casual (e.g., polo shirts and khakis) or coveralls or jeans.
When my grandfather died in 1973 -- I was 14 -- I wore a dress to one day of the wake (we always did two days back then) that would not have passed muster as "funeral wear" in many circles today, because it was so short. But that was the skirt length of the day. It was not low-cut; all it exposed was leg. And I wore hose.
I did wear black to the last funeral I attended, but that's only because I own a set of suit-like-looking separates that happen to be black. If they'd been navy or maroon or forest green, I'd have worn them without a thought to the fact that they weren't black. I've only seen "all must wear black" funerals on TV -- with all the women in not only black dresses but black hosiery and black hats with veils. Have never seen such a thing IRL, and I've been to a lot of funerals.