I am between a size 4-6 or a size S in womens tops and I am 56 32DD. I purchased the small and medium. While both fit, the medium had more room in the chest area which was very noticeable with a bunching or material where the arms and chest meet. This did not happen in the small.
I love the white color, however it is pretty see through. I already planned on wearing a bikini underneath, however it will be very apparent what color bikini you have on. The purple (more a violet on the red tone) is completely opaque. While I prefer the white, Im pretty sure its not going to be able to be worn to the beach. I cant imagine it staying stark white after a day in the ocean / sand.
I wish there were other color options that weren't so vibrant! Something more muted would be nice. I could see owning a few colors of these for such a good price.