The detailed description is here.
In all methods of color setting the aA parameter is added, it has values from 0 to 255. 0 - transparent drawing, 255 - transparent. Default value is 255.
In the Stream.mq5 file (script) is given the example of drawing with transparency.
Translated from Russian by MetaQuotes Software Corp.
Original code: https://www.mql5.com/ru/code/1556
The Acceleration/Deceleration Indicator (AC) measures acceleration and deceleration of the current driving force.Average Directional Movement Index (ADX)
The Average Directional Movement Index Indicator (ADX) helps to determine if there is a price trend.