Decades of research has developed a system for revealing and exploring music harmony. This science has been discovered from its core.
Decades ago, we came across an article of harmony theory introducing the idea that color and music can be connected through the modal-scales of harmony, since they have a mood aspect. The colorfulness of modes was recognized by the earliest of composers, though was not acknowledged by harmony theory until recently, and with the development of this new system.
Using the graphical piano above, one may play a color-note (left hand) as a bass note, and hear the impression of the related mode as they perform (right hand) upon the white keys of the 'key of C'. The bass note creates a point of view from which the color or mood of the mode is observed, and this happens regardless which higher notes are being played. Next, we learn the modes as scales so we can remember their structure.
A 'musical spectrum' is seen when the main melodic scale is regarded in two directions: The perfect 5th (or 4th) and the chromatic (half step) are the only two intervals that cycle through the 12 notes. These two intervals create two dimensions, each involving 12 positions: One accounts for the Circle of 5ths, while the other parallels the Chromatic Scale on which instruments are played.
The above spectrum shows the seven primary modal-scales, all aligned under the note G for this example. Each mode can be translated to its related key-signature by following from left (lower notes) to right (higher notes). In this system, the Natural Major Scale of a key-signature is always the Orange Mode; the Natural Minor Scale is always the Blue Mode. It is easy to learn the seven primary modes since each mode has only one note different than the mode of a nearby bass-color.
The first level is to get to know all 7 modes in each of the 12 key-signatures, which chords accompany those modes, and how the modes fit together in one key to make a song. The guitar benefits most from this color system, since it is the hardest to learn due to the way it is tuned; meanwhile, a piano provides the most simplified view of the forms of harmony. It is recommended that every musician is acquainted with drumming and also the piano keyboard.
Beyond composing / improvising with these seven primary modes of each key signature, moves us to the intermediate level: There we learn about how to change key-signatures within a song, and how to combine scales in order to use more notes.