Whoops, so she was. Sorry.
Nevertheless, I think the point applies to livery, also. “White” in terms of textile colours, before modern chemical bleaches, wasn’t nearly the snow-white we now assume, and very often meant simply the natural colour of the wool/cotton/linen. Futhermore, before dry cleaning, white woollen garments couldn’t be washed and so could get pretty grey with age. Conversely, all but the very best and most expensive black dyes faded to dark grey pretty quickly.