The indicator was described by B. Williams as fourth dimension - Trading Zone:
If the current bars of AC and AO are green, it shows that the zone is green.
If the current bars of АС and АО red, it shows that the zone is red.
If the bars of AC and AO are differently directed then the bar is colored grey (grey zone).
Translated from Russian by MetaQuotes Software Corp.
Original code: https://www.mql5.com/ru/code/8534
It represents a standard MovingAverage indicator with the function of smoothing by the second-order Butterworth filter added.GRFLeadingEdge
Indicator of Bollinger bands.