Quick Answer: The color of a knob's rim indicates how conventional or unconventional the setting for this chord is, with colors ranging from green to red.
Color indications in a knob's rimWhen opening a project or a template, Liquid Notes performs a harmonic analysis of your MIDI arrangement that reads and interprets it like an expert composer does. Thereby, it will detect chord boundaries, correlations between notes, etc. - upon which a matrix of possibilities for chord substitutions is calculated. Depending on where a particular chord lies on this scale, the software can map it into a color coding (from green to red) that represents conventionality of a chord from a listening perspective.
Hence, a green rim indicates that a chord is conventional. Whereas a red rim indicates a very unconventional chord, having reached the other end of the scale. Similar to a traffic light the color code of the rim moves from green over orange to red.