It's not actually about the color, it's about the luminance. The yuv-chromaticity is the range of possible colors that can be created by mixing different levels of luminance. It's like a big ol' spectrum of brightness.
Imagine you're a color theorist stuck in a world where the only colors you have are shades of gray. You're like, "How do I make a pretty picture with just these dull tones?" And then, BAM! You discover yuv-chromaticity. It's like the secret ingredient in your favorite recipe. You're like, "Oh, I can make a whole rainbow with just this!"
Now you can make your pictures look like they were painted by a kindergartener, but with more gray.
Want to learn more about yuv-chromaticity theory?
Or maybe you'd like to see some yuv-chromaticity applications?