Unless there is an add-on already doing this, you need to do some programming.
This is what I think you need to do:
- Subclass or make a new portlet type.
- Add the 'color fields' to it
- Install the colorpicker add on (note: this add-on is not working on Python 3, I think my fork does: https://github.com/espenmn/collective.z3cform.colorpicker )
Another option could be to define some colours to use and use a select field. (in other words, a select field with values like 'green', 'blue', 'red' etc. This approach is probably easier and you can just add the selection as a class in you browser view.