How is the author's name given a different color?

Author's and visitors' names use the same color in comments.The point here is that the color of the author's name is different in the comments. For example, in visitor comments, name is red. But, the name of the site author should be gray. (Only in comments)

I know an ID needs to be added for the author's comments. However, I could not add this ID. Therefore, the style I gave in style.css does not work either.

I just tried this in css, but that didn't work.

.comment-list .bypostauthor .fn {color: gray;}

How can I achieve this?