The most popular color space supported and the one that BT.601 prefers is the YCbCr color space. Where Y equals the luma component and the Cr or Cb equals the chroma component. These signals are generated via RGB in a mathematical relationship and they are highly uncorrelated, which means that they provide much better compression characteristics than RGB information does. That’s one of the key reasons that this color space is so popular, and is recommended by BT.601.