A Riot of Colours

I never did get this: why is a bunch of many different colours a "riot"? What? Are they going to rebel?

And when the sunlight struck the window in full force, the coloured glass in it threw forth multiple points of glittering light.

The blues, reds and white decided to get together, against the reds, yellows and greens, throwing the world of colours into great disorder.

Blue: Hey! How come you're on their side too, Red?

Red (to great protest from the oranges): Why ever not? Being on both sides is also a side.

"If you want to talk about sides, then technically, you all should be on mine," adds White.

Red and Blue: Shut up, you!

"If we get together, we can unite and stand against Black," White continues, albeit sulkily.

Hey! Don't get me involved, I'm not a colour! - Black.

Thus, the colours went back to rioting...