My question is almost identical to this one: How to add some extra fields to the page in django-cms? (in django admin panel) but notice the "add page form".
I liked very much the Ben Davis's answer: https://stackoverflow.com/a/15371900/1685973 but it does not add the custom field (named "color_scheme") in the "Add Page" admin form... That's what I would like to have :-).
(I would have added a comment instead of asking a new question if I could, but I do not have the required 50 points to do that)