I am trying to change the color of the area of the custom shape made using the Query Widget in experience builder. You can pick different shapes under "Geometries from a map" option. By default it uses a purple shade. I can't find any way to change the color or transparency.
In the Query Widget Settings Panel, go to Action > Data Action. Open up Show On Map and select Use Custom Symbols.
Clicking on one of these shapes should bring up another menu for changing color and transparency.