Minor documentation omission (I think): underlined words

The documentation I’ve seen says (as I understand it) that words start out blue, become yellow, then become “white” (i.e., not highlighted). It seems that words of status “learned” are not highlighted but are underlined. It took me a while to figure this out. Perhaps it could be inserted as a sentence into the documentation somewhere; or perhaps you can point me to where it is currently documented.