There are endless ways to use it, depending on your ideas.

For example, your opponent called on your double barrel on the turn.
You can think about your opponent's expected range in this case by coloring.

==Recommended for situations like this==
You want to learn the preflop range by coloring.
You want to visualize your opponent's expected range by coloring.
To visualize where the lower limit of value is on the river Visualize the lower limit of value on the river with a range chart.

Think in ranges and stand out from your rivals in the world of poker.