Introduction to Philosophy/Aesthetics
Humans divide objects which they observe into categories. According to one definition, Philosophy is the discipline of how humans determine these categories, communicate about them and interact with them.
Aesthetics is the sub-discipline of philosophy which acknowledges that humans interact with their environment in the context of sensual experiences.
These experiences include color and sound. A question which is fair game for Aesthetics might be: "What combinations of notes sound good together?" This is an old question and may demonstrate various trends in philosophy. The answer to this question changes over time. The categories of which chords sound good and which sound bad have changed over time.
Another similar question is which colors look good together. This is completely analogous to the above question about musical harmonies. One may also ask which colors or sounds may easily be distinguished.
A philosopher who is inclined towards linguistics may take the result of these inquiries and ask what languages are possible given the combinations of symbols such as colors or harmony rather than the symbols of distinguishable vocal utterances.