Yes, magenta and green lines appearing in unflattering ways are a direct result of digital video capture. This is called chromatic aberration and it is is most noticeable in high contrast shots where clipping highlights and crushed shadow information of digital video meet. For example, the text you mentioned may have been white text over a black background creating slight aberration. Other scenes with aberration can include exteriors with bright skies and dark subjects. The characters in these circumstances can suffer from chromatic aberration from clipping skies. The aberration is not limited to lines. Because aberration is a result of picture elements meeting at vast exposure levels, the aberration will form around subjects, buildings, etc. In this case of The Hobbit, where the majority of the film was shot in studio with keyed in skies, you may have also been experiencing a fringe from the key, where the editor replaced the green screen on set with their CGI backgrounds. Because aberration is attributed to exposure, the film's frame rate had no effect on the level of chromatic aberration.
