How do I (33M) tell my wife (33F) that the outfits she thinks are “sexy” aren’t “sexy”?

I find my wife beautiful and very attractive. We have been married 6 years, together for over 10. She is capable of being VERY sexy – she has dressed up in the past for dates etc and she looks gorgeous. She has a shimmery black dress that she wears with tights and heels, very sexy. She has a longsleeve, high-neck green dress that she wears with boots, very sexy. She has a pair of leggings that she wears with a white blouse/shirt thing, very sexy. She wore a t-shirt once with jean shorts, and black tights underneath, with converse shoes, very sexy. I can keep going. EVERY time she has worn these things, I have EXPLICITLY told her she looks amazing and sexy.

However, when she wants to do something nice/sexy for me in bed, she puts on outfits that are…not very sexy. I don't know how else to describe it. She has this leopard-print top that is like almost a "wife-beater"/tank top. It's not very flattering on her, and it looks tacky. She has this nighty/dress thing that is almost like a beach cover to wear over a swimsuit? Idk. She wears it when she's "trying" to be sexy for me but it's really not good on her. OF COURSE I am still aroused by her, and I recognize and appreciate the effort, and we have good sex. The clothes come off anyway so it really doesn't matter too much, but here I am I guess.

Anyway, I rambled a bit, but the point is this: my wife is absolutely capable of being insanely sexy. However, the things she THINKS are sexy on her just aren't, and I don't know how to tactfully tell her. Sometimes she gets shy/uncomfortable about talking about sex things, so I really want to be careful in how I approach it. Thanks!