Just cos I find it interesting,
The three colored RCA jacks are actually not RGB. They are component video, which shows all (visible) colors into two color maps and one luminance (brightness) level.
On this image from the
Wikipedia page on YUV color, you can see how the three different levels map to a single color image.
This approach saves bandwidth because less room can be devoted to the color spaces. Then it also works well with human perception of color, even when broadcast screws things up. So it's a remarkable olden times analog hack.