This is yet another version of Express Stave. It uses the same notehead shapes as the “6-6 jazz font” and “reverse-color” versions of Express Stave, as well as Keller’s novel clef symbols (shown on the “reverse-color” page). The only difference is in the notehead coloring scheme. Whereas other versions of Express Stave use a diatonic coloring scheme, distinguishing the white and black keys of the piano, this version uses a “three-color” scheme, in which noteheads with a staff line or ledger line through them are considered as a shortcut for gray. The three “colors” alternate in regular succession as one moves up the chromatic scale. Thus each of the three diminished-seventh chords consists of notes that are all the same “color.” This coloring scheme is similar to that of Roy Pertchik’s trichromatic keyboard layout and Joe Austin’s ChromaTonnetz notation. Note that Keller prefers the 7-5 approach to notehead color, as used in his other versions of Express Stave.
Source: John Keller. Express Stave, Tricolor version introduced September 16, 2010.