I will dress in bright and cheery colors, and so throw my enemies into confusion. All bumbling conjurers, clumsy squires, no-talent bards, and cowardly thieves in the land will be preemptively put to death. My foes will surely give up and abandon their quest if they have no source of comic relief. I will not fly into a rage and kill a messenger who brings me bad news just to illustrate how evil I really am. Good messengers are hard to come by.
Morale is better with a more casual dress-code.
Similarly, outfits made entirely from black leather will be reserved for formal occasions. I will not turn into a snake. It never helps. I will not grow a goatee. In the old days they made you look diabolic.