Found: 5.3.0
Ext.NET forums' thread: DropDownField with ColorPicker not work in Safari

Using macos' Safari browser, if a color picker component (<ext:ColorPicker />) is defined within a Dropdown field's container/panel, the former's Select event won't trigger on click, but the dropdown gets dismissed (a tap event does trigger) thus becoming impossible to make a selection from the dropdown field.

Using the advanced color picker's <ext:ColorField /> (outside a dropdown field) works fine and may be an acceptable replacement for the simpler component.