I don't understand what is needed- if I watch a show do I click to change color (black and blue) or do I click on it if I have not watched the show yet?
If you want to follow a series and to show up on your calendar/watchlist, you either click on follow on the specific series page or click the heart on the poster in the shows page (if the heart turns Yellow, it means you're following it). When you have watched an episode, you could mark it by using either the watchlist or click on the eye in the episode page. A black eye means you haven't watched it as of yet, but when you click that eye, it turns green/blueish, which means you have watched that episode.