Create a color field for content and set it to be required
Open an article to edit and view the source
You will see <input type="text" name="jform[com_fields][colour]" id="jform_com_fields_colour" value="none" placeholder="#rrggbb" class="minicolors required" data-position="default" data-control="hue"1 data-format="hex" data-validate="color"/>
Note thedata-control="hue"1 the 1 should not be there
Then something's not right, you're removing $readonly and $required variables which tells me that neither of those attributes should be in the resulting output unless they're being attached to something else, which seems wrong too. Either way I can look more later too, about to leave for work.