These candles can be used to identify previous small lasting and long ranging trends. Areas that are heavily saturated with one specific color will likely indicate a trend.
If you are not able to see the colored candles, disable your main candle overlay in the top left by clicking on the eye icon.
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.