を着ると

when wearing

→ を
phrase Rare #30,492
when wearing と marks a condition or situation, often translated as “when” or “if.”
JA: このコートを着ると暖かいです。
EN: When I wear this coat, I feel warm.

彼女は白を着ると魅力的です。

She looks attractive in white.

そのドレスを着ると素敵よ。

You look lovely in that dress.

確かに彼女は和服を着ると美しく見える。

It’s true that she looks beautiful in traditional Japanese clothing.