Color the notes of each voice
This plugin colors the notes (and in the 2.0 version the rests, stems, hooks, dots, accidentals and stem-slashes too) according to their voice. The color scheme is the same as the toolbar:
Voice 1 - Blue, Voice 2 - Green, Voice 3 - Yellow, Voice 4 - Purple
This plugin has a version for MuseScore 1.x as well as for 2.0!