The histogram represents the distance between the DI+ and the DI-. The crossing of the histogram is equal to the crossing of the DI lines.
The line is coloured based on the threshold.
This creates a clean representation of the + DI.
In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.