The color picker is a feature that can be used by websites in their forms. I don't think it can be called up outside of that context, unfortunately.

The questions/987622 was marked as duplicated from this topic, in that question there was more information:

the update says there is a color pick for the widget on Firefox beta but it won't pick up. Either my phone sucks or the update didn't take. Or maybe j just don't know how to mess with that.

The color picker is a new html form element.

   <input type=color>

You can find a demo of input color in form number 7 at http://cdn.sixrevisions.com/demos/0345-new_html5_form_input_types/new-html5-form-input-types.html