As a start, I quote from the erotic novel “The teacher in the sex trap!, Part 1” by an author who has chosen the pseudonym Caroline Milf for herself. I use the example because the author does not only describe the shape of a breast with one or two keywords but takes her time for the description.  The color and shape of the breasts themselves she describes just as clearly as those of the nipples, painting a picture that definitely sticks after reading:

Just at that moment it happened that one of the boys took off little Asena’s brassiere, because when I looked through the keyhole again, the young Turkish girl was sitting blithely, without shame, without embarrassment, with her upper body naked in front of the boys. She had really cute, incredibly pointed breasts that stood up steeply. They were almost as well tanned as the rest of her upper body, but her nipples were of a surprisingly bright red, and they were already protruding a little bit. 

Caroline Milf: Der Lehrer in der Sexfalle!, Teil 1

This takes her one step further in the question of how to best describe a bosom. Caroline Milf takes four steps in this short scene:

• She describes the shape of Asena’s bosom as “pointed.” We had already thought about the shapes a breast can take yesterday, so I won’t say much more about that at this point.
• She goes into the skin color and distinguishes it from the color of Asena’s other body.
  This will be another special topic here on the blog, especially since the skin on the bust itself is often two-colored, due to the wearing of bikinis.
• It goes into the color of the nipples.
  This will also be a detailed topic here in the blog. Because with the color the entire color scale is conceivable from the tender salmon pink up to a strong dark brown. Makes sense to take a closer look at this palette.
• It addresses the shape of the nipples.
  Caroline Milf just hints very effectively here, “her nipples were of a surprising light red, and they were already protruding a tiny bit. “
• In addition, the size of the areolas varies, not to mention the shape of the nipples themselves. Did I mention slip nipples? The fact that in some women the areolas grow when aroused?

If you now feel like describing something other than 08/15 breasts in your next erotic story, you can use the breasts from the breast gallery of the website “007 Breasts” (007b.com/breast_gallery.php) as inspiration. In this gallery, you can find selfies of various women, commented by themselves. In these pictures, the range in shape and color becomes nicely clear.

The breast gallery of “Bravo” (bravo.de/dr-sommer/brust-galerie-schau-welche-unterschiede-es-gibt-172473.html) is a bit more standardized. The pictures here are supplemented by explanatory texts about the developmental phases of the breasts.