keylight - screen balance

hi
i am reading the keylight user guide.
Was wondering what is the screen Balance exactly.

* WHAT IS THE PRIMARY COMPONENT?
* WHAT IS THE OTHER TWO COMPONET?

I don t really get it
please feel free to check what the guide says

The guide says :


Saturation is measured by comparing the intensity of the
primary component against a weighted average of the two
other components. This is where the Screen Balance control
comes in. A balance of 1 means that the saturation will be
measured against the smallest of the other two components
in the screen colour.
A balance of 0 means that the saturation will be measured
against the larger of the other two components. A balance of
0.5 will measure the saturation from the average of the
other two components.

33
The appropriate balance point for each image sequence you
key will be different depending on the colours in that image.
Generally speaking, blue screens tend to work best with a
balance of around 0.95 and green screens with a balance of
around 0.5. These values are selected automatically the first
time you pick the screen colour. If the key is not working too
well with these settings, try setting the balance to about
0.05, 0.5 and 0.95 and see what works best.