There was however a bug in the code that prevented the candle from turning grey when the volume bar did so.
To solve this bug you can open the script and change line 209 from:
if (paintbars && bc > 0) BarColor = Plots[bc].Pen.Color; // paint the price bar
to
if (paintbars && bc >= 0) BarColor = Plots[bc].Pen.Color; // paint the price bar