What does the word "Chroma" actually mean?
 

Does the word CHROMA refer to just colour when it deals with video?

chroma |ˈkrōmə| noun purity or intensity of color.

ORIGIN late 19th cent.: from Greek khrōma ‘color.’

In video systems chroma is the part of the signal that represents color; it's the color difference components of a video signal. You can get the numbers in a book like Charles Poynton's. Color and luminance is not separated perfectly... the wikipedia entry on chroma subsampling should have links to that information.

2- In the Munsell color system, chroma refers to the purity/saturation of a color. It is a slightly different concept. In video no one really talks about that color specification system.

3- There's a difference between chromaticity and chrominance (chroma is similar to chrominance)... the distinction of which is important when reading vectorscopes. Both refer to color. If you for example change the exposure on a camera, chrominance will change but chromaticity will stay the same. You can think of chrominance like "colorful light energy" that adds colorfulness to light... so if you change exposure, the overall energy changes and therefore that's why chrominance changes.

Intuitively when you think about color, chromaticity usually makes more sense. In some cases the distinction is not important.

You guys are smart! I thought "chroma" was all the shiny silver stuff on Italian sportscars!

:-)

Chroma, pffft!

The only thing that counts is progressive scan, baby ;)