JPEG
JPEG also uses three bytes for every pixel each, but it's using the YPbPr (also known as YCbCr) format. Here, the first byte tells us how bright the pixel is. The second byte tells us how blue the pixel is. The third byte tells us how red the pixel is. Using this colour format, the brightness is stored apart from the colour. This is useful, because we are going to compress an image. Because the human eye is better at seeing brightness than seeing colour, we can apply a greater compression to the colour bytes (the Pb-byte and the Pr-byte). Since we see brightness better, we use less compression on the Y-byte, to have the image look better after compression.