I wrote the explanation above on component video from memory, and it's not entirely correct. Here's an explanation taken from
Projector Central:
"So how do you transport an image from the camera to your TV or projector? You could transmit it in the RGB format in which the camera first captured it. However, RGB is a bandwidth hog and bandwidth is expensive. So the first thing that happens is RGB is converted into a more compact format. This format is component video.
Component video consists of three signals. The first is the luminance signal, which indicates brightness or black & white information that is contained in the original RGB signal. It is referred to as the "Y" component. The second and third signals are called "color difference" signals which indicate how much blue and red there is relative to luminance. The blue component is "B-Y" and the red component is "R-Y". The color difference signals are mathematical derivatives of the RGB signal.
Green doesn't need to be transmitted as a separate signal since it can be inferred from the "Y, B-Y, R-Y" combination. The display device knows how bright the image is from the Y component, and since it knows how much is blue and red, it figures the rest must be green so it fills it in."
Here's an explanation of why RGB is superior to component video taken from
CRT Projectors Co UK:
"Q: Why is RGB superior to Component video?
A: Component video takes advantage of the fact that the human eye is very sensitive to changes in luminosity but not very sensitive to colour. Component video uses the full luminosity bandwidth but a reduced colour bandwidth so that the electronics can be of a lower specification than required for RGB. Basically its a cost reducing exercise for manufacturers, high video bandwidth requires high quality (read cost) electronics. The theory is that while Component video uses a reduced video bandwidth, the human eye can't detect the difference in the final image. Most of the time this is true, but remember the native format of any projector is RGB, if you use Component to the projector it still has to be transcoded to RGB to drive the tubes. This transcoding can introduce errors, so use RGB where possible to reduce such errors."