I’d really like to know a solution for this as well. Running AE 2020 on Windoze 10. I have the Edit>Preferences>General>Use System Color Picker, unchecked and I get the standard system colorpicker. Tried clicking it on, running, click oit off running, restarting and nothing but the system color picker.
Strange, and unhappily thing, is my c SDK scripts always brings up the correct/AE style colorpicker. I find it really hard to believe that after all these years its not exposed as a core ScriptUI/ExtendScript control.
Before someone asks why then don’t I just work with the SDK? A day to right a good script for a project versus several with the SDK. That and a bottle of aspirin (spent to much time in Python the last few years and it’s corrupted my c/c++ desires).