Captain Yonoi painted face

There might be other reasons. Possible motivations:

Before the end of WW2 Japanese men wore makeup to improve their appearance (at least according to Yukio Mishima in his "Hagakure Nyumon"); hungover or tired businessmen would wear blush or concealer to hide their state. Western cultural norms imposed during the postwar period led to a cessation of this practice.

Before battle, samurai would accent their faces with makeup. This was done so that if they were killed in battle and their heads were severed and displayed, they would appear youthful and healthy rather than pale and sickly.

The actor who played him was also, like Bowie, an electronica musician famous for wearing androgynous makeup when onstage. Perhaps it was to allow the audience to more easily identify the actor/musician?

Traditional Japanese theater is primarily divided into Noh (which deals with tales of the supernatural) and Kabuki (which deals with heroic stories). If Yoroi is supposed to be a Kabuki character, it would require other signifiers like wardrobe and props. Perhaps Yoroi is being depicted as Bishonen (androgynous male character) to show his embodiment of Japanese cultural ideals, much as a European chivalric knight would be depicted as muscular and handsome. The Japanese hero Minamoto no Yoshitsune is often depicted as bishonen.

Homosexuality was viewed in contemporary Japan as being an ideological split between the duty and loyalty owed one's lover and the duty and loyalty due to one's master or lord. Yoroi is supposed to have a split sensibility between his unrequited love for Jack Celliers and his sworn duty to the Japanese Empire and its culture. Perhaps it is to show his split nature?

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