Women's Investment Banking Attire

I'm starting a summer internship in investment banking at an American bulge bracket bank soon, and have been having a hard time figuring out exactly what kind of things are appropriate to wear. I'm very slim and not very curvy at all -- most of my clothes now are fitted sleeveless dresses in dark colors, knee-length, from stores like Reiss and Theory. I've paired them with typical conservative blazers for interviews.

More recently I bought a "relaxed blazer" -- basically it doesn't have buttons, is kind of boxy, is a bit shorter than the average blazer and has ¾ sleeves instead of full-length sleeves. I uploaded an image. Is that sort of blazer work-appropriate?

Also, in general, how conservative should colors be for women? Is a color like cerulean blue too flashy for a dress? Will I be called a funeral director if I wear a black dress with a black blazer?

I'd really appreciate any thoughts anyone might have!