The Zone is mention in New Trading Dimensions by Bill Williams,PhD.
The Zone is used for Entry Signal
Green Zone are painting Green Bars when Awesome Oscillator (AO) and Accelerater/Decelerator (AC) are both increasing.
Red Zone are painting Red Bars when Awesome Oscillator (AO) and Accelerater/Decelerator (AC) are both decreasing.
Gray Zone are painting Gray...
Double Stochastic is use 2 Stochastic for monitoring price swing.
Slow Stochastic (21,3,3) for monitoring the swing of price cycle.
Fast Stochastic (5,1,1) for monitoring the swing in price ripple.
When 2 Stochastic run way from each other, separately , mean Price will move only retrace or rebound in ripple movement.
When 2 Stochastic Flip and Run break thru...