Having visibility of where a series is increasing or decreasing can be useful. For example, to see exactly if a moving average is advancing or declining.
This is an indicator on indicator script that will essentially cover (plot over) the source series with the same values, but colored different depending on whether the difference between consecutive values is positive, negative, or neutral.
For this to work cleanly, you may need to hide the source series, if there are colour clashes. By default, we also use a fairly thick line to plot, to show the visual effect more clear