I've asked the same question before. And the respond from my British teacher was :" SOMEBODY is the face of Hugo " be the face of （如果你想问的是某某是某某品牌的代言人的话）

代言人 = spokesperson 代言 = （verb) to speak in behalf of

代言 (noun) = advocacy; pleading by proxy; speaking for another; attorney 代言人 = an advocate; a lawyer

To be a spokesperson. 這是‘當發言人’ 的意思嗎？