Itachi would be one of, if not the best mentors to have tutelage under. Kisame I see more as a mercenary trainer, than an ordinary shinobi. Both have the commitment, and overall esque for the job.
Those aren't ranked from weakest to strongest. It merely is explaining as to what each color means. Though I agree FemmeFatale's statement is false.
If it were in order in regards to which was stronger, Green would be a lot higher, seeing as the Eight Inner Gates last gate opens using the Death...