Is there a way to customize highlight colors in Preview (Mountain Lion and later)?
What they are talking about is having more color choices for highlighting text than are available by default. Both the Yosemite choices in your post and the Mavericks choices (see below) limit the user to 5 preset colors. There doesn't appear to be any way to use the OS-built-in Apple color picker to choose anything other than this very limited set. Very frustrating.