As far as I can gather, the black tie protocol is breaking down.
I was asked to do a reading at a relative's funeral where it was a directive from the deceased not to wear black, but then another older relative was critical of me for not wearing something black - he wasn't impressed when I pointed out my shoes were black.
I've seen people wearing black ties and also black armbands, but I think your tidy presence is more important at the end of the day rather than what colour you have on.