。
She prefers subdued colors.
Literal
She [topic-は] plain colors [object-を] prefers.
地味な ('plain / subdued / understated') is a na-adjective that describes things without flashiness — the opposite of 派手な ('flashy/showy'). 好む ('to prefer / to like') is more literary and deliberate than 好き — it implies a considered preference rather than a casual liking.