What are the PAT volume bars telling us?
The histogram that you see at the foot of the PAT chart is a record of Pvol. We call it Pvol which is short or PAT Volume. The Forex market does not provide volume, however, PAT takes volume from different areas of the market to produce volume that is relative to the forex market.
The visual representation of the volume is coloured blue and green as default (You can change this if you wish to personalise your charts)
Why two different colours?
This is a pure aesthetics' setting to visually aid the spotting of increasing and decreasing volume. If you see a Blue histogram line then this says the volume on THIS line (and therefore the bar above that is relative to this line) is GREATER than the volume on the preceding line/bar.
So in summary:
A blue line is showing increasing volume over the preceding line and a green line is showing decreasing volume over the preceding line.