In chapter 10, as the party is leaving Southerton, Mrs Norris says, “…That Mrs. Whitaker is a treasure! She was quite shocked when I asked her whether wine was allowed at the second table, and she has turned away two housemaids for wearing white gowns.”

White clothes were generally, but not solely, worn by the upper classes. Servants did not wear white because it was much more apt to show dirt and need more frequent washing. This fact probably evolved into a hierarchy of clothing, in which white indicated a class of woman who was not required to do work. A servant wearing white would look “above her station.”

Let me recommend The Dress of The People by John Styles, an excellent book on clothing in 18th Century England.