Comment by adornKey

The article skipped a bit on explaining the CIE-XYZ space. Although it is quite simple.

There is one axis Grayscale - that gives you the Brightess value. You can use that for black/white TV.

Now for colour you have 2 dimensions left. For these you pick one axis, where the eye is most sensitive - and perpendicular to that you have one axis, where the eye is least sensitive.

This colour space is the oldest and all axis there make sense. You can easily compare brightness, and you e.g. can assign more bandwidth to the sensitive colour axis if you want.