To support JDK-8160837 : WebEngine doesn't handle html5 color picker. WebView requires a Custom Color picker dialog with Two Buttons (Ok and Cancel) and Color picker widget.
CustomColorDialog would be best option to re-use in WebView With below modification.
1. Hide Opacity Button and its slider
2. Hide Use Button
3. Save button text to be as OK ('Save' --> 'Ok')
The above there modification will make the Common UX behavior observed in Windows (Firefox and chrome), Ubuntu (Firefox and chrome).