4. At funerals, wear black only.

Reason: It’s solely for grieving.
Princess Diana was an exception to this rule on occasion.
Royals have traditionally only worn black at times of sorrow. Princess Diana, who occasionally disregarded this restriction for formal events, attested to this. In an early interview, the late Princess stated that her then-husband, King Charles III, took issue with her outfit choice.
At funerals, wear black only. ©Christopher Furlong/Images Gettty
Diana claimed that Charles once made fun of her for showing up to a royal function in a black dress, stating, “You’re not going in that, are you? People who are grieving only wear black. True to usual, Diana wore it nonetheless.