I've been reading a book called Justinian's Flea: Plague, Empire, and the Birth of Europe, by William Rosen. The author tells of some of the activities in sixth century Constantinople at the Hippodrome. Ostensibly a place for racing horses, the Hippodrome was the "main drag" of the city in its day. Actors, animal acts, music and such entertained people in between races. The teams of racers were identified by colors; everyone from charioteers and groomers to all that team's supporters wore the color of his or her team. Four teams wore red, green, blue or white. Eventually the Reds were absorbed into the Greens and the Whites into the Blues. The Emperor Justinian tended to favor the blues.
In 432 C.E. the city, beginning at the Hippodrome, broke into rioting, along color lines. Riots were not uncommon and always began at this gathering place. They were often about theological minutia. This particular riot, called the Nika (meaning "win" or "conquer") revolt, began as a result of a murder at the Hippodrome; it lasted an entire week and resulted in the destruction of buildings, including the Hagia Sophia*, and the deaths of thousands. Nearly half the city was destroyed.
How like this are the Crips and the Bloods; the Union Blue and the Confederate Gray; red and blue states; dark- and light-skinned people. In the case of the Blue and the Gray, we had the Civil War. Other colors are associated with fighting and assassination. We sometimes read of teens being shot down because they were wearing red (or another color of the despised "other").
Schools have their colors; my high school in New Jersey had maroon and white -- "Maroon and white, maroon and white, fight, team, fight!" In PE class we girls were teamed for drills; we wore pinnies of one color or another.
Teams have team colors -- to identify them on the field, one would suppose, although they sometimes have direr meanings. Fights and riots are not uncommon in competitive sports.
I've witnessed Pagans endlessly debating whether they should wear Roman collars (utterly stupid, IMO) and if so, whether those collars should be green for Nature or purple for "spiritually evolved" or some other color.
How helpful is this, I wonder.
When we celebrate the Feast of Brigit, we ask celebrants to wear white, gold or yellow, or red in her honor. At the Full of the Moon, I like to wear white, and at the Dark, black. I love to dress in the colors of the season or the deity I'm honoring. I think dressing in colors, using appropriately colored altar cloths and candles, along with incenses and foods and music, helps the resonance with what we are doing.
Overall, I like to think I live in a rainbow world.
* The Hagia Sophia was rebuilt by Justinian in only five years.