The status is essentially represented in the color of the quality tag behind a movie name, as can be seen in this picture:
Forgive the bad movie choice, this CouchPotato installation is shared with my little brother
Many people apparently are looking for it and I couldn't find it as well, even though I feel like it is an essential part of what makes CouchPotato such a great program.
Well, I was looking for this as well and didn't find anything anywhere, so I investigated it myself using FireBug.
In the CSS of CouchPotato the following colors are present. Because the CSS classes have meaningful names, I'm quite sure the color codes are as follows:
I also was wondering why I was seeing the red color I hadn't seen before. After seeing the two different shades of green and their meaning I realize the red marking shows up when I manually remove a Torrent before CouchPotato thinks it is done seeding. The Torrent then goes 'missing'. CouchPotato doesn't rename and move the movie files automatically when a movie is in this state, so you'll have to manually mark the movie as 'done'.
Another thing I found in the CSS was the 'finish' class which adds the checkmark image to a quality, meaning CouchPotato will stop looking for a better quality release after it has found this quality.
This can also be found in the settings.
I hope this is helpful.