If I dress in the same style as my ex-boyfriend's girlfriend, I will still like it when he sees a smile.

What you want to say is, are you going to learn from his current girlfriend to save him?

The answer is no,

First of all, I think you broke up because of your style of dressing, right? There must be other wishes, right

Second, he already has a girlfriend, which means he doesn't love you anymore. Since he doesn't love you, how can he love you again just because you changed your dress style? If he really likes you again because of his dressing style, then I also advise you to leave him.

If you don't want him back, you have already broken up, so you don't have to care about his eyes, because he is not the only one for you.