Here's the original source with brief explanation for each one. Here's /r/fashion 's critique of the historical accuracy. The biggest criticism is there's no way Pocahontas would have worn something that skimpy. In addition a lot of the styles are still so generalized that it's no more accurate than the Disneys version.

I'm not familiar with Native American clothing, but personally I find Ariel's dress bothersome. Specifically the weird pointy hem which seem out of place with something from that period. In addition Belle's bright color scheme seem strange with 1700's fashion, which was dominated with soft pastel color. Belle reminds me of Madame Du Barry from the 2006 movie Marie Antoinette. The director specifically made her brunette and wore loud and bright clothes to make her stand out from the rest of the cast and show that she is a rude bitchy outcast even though her ensemble is not very historically accurate and seem out of place.

Just some words on the ancient greek one: The basic idea of the figure's peplos is quite authentic if you compare it with hellenistic statue types. In every case it's much better than the original Disney character. However, I have no idea why they chose this hairstyle which isn't very similar to anything I know about ancient greek hairstyles. The hairstyle might refer to similar ones in attic red-figure vase painting on a very excessive level. Generally, it is obvious that they chose very high level of stylization and I won't criticize this point as it's understandable that they wanted to stay comparable with the Disney originals.

Edit: Did some research on the hairstyle.