In essence, it implements the idea of visual interpretation of the state of the fourth dimension of the Chaos Theory by B. Williams - Zone.
Information on the Chaos Theory in general and the on logic of determining its state in particular can be found here.
In short, the state of the zone is determined based on the values of two indicators: Awesome Oscillator and Acceleration/Deceleration. Both are included in the standard package of the MetaTrader (Insert - Indicators - B. Williams).
When the driving force (Awesome Oscillator — AO) and acceleration (Acceleration/Deceleration — AC) are in the same direction (both green or both red) — it means that the driving force not only moves in that direction, but also accelerates.
If the current AC and AO columns are green, this indicates the green zone. For clarity, this bar can be colored in green.
If the current AC and AO columns are red, this indicates the red zone. For clarity, this bar can be colored in red.
If the AC and AO columns have different directions, the bar is colored in gray (gray zone).