Yes. I truly had no idea about the colour thing until I read it on Mumsnet in my mid-30s (which is years ago now).
I'd just never been especially interested in weddings, wedding culture, etc. I'd been to lots of weddings as a guest and even been a maid of honour once, all of which was perfectly OK but I just never happened to hear anyone observe that this colour issue would matter.
It would never have crossed my mind independently because if I'd been getting married myself, I wouldn't have cared what other people wore.
So in my ignorance I did once go to a wedding in an off-white shift dress, partly hidden under a pale green cardigan. It was the late Nineties. No idea whether anyone took umbrage.