[XeTeX] Change fonts for different environment/commands

[Arthur Reutenauer]

>                                  except for the number in footnote -
> it stays black

  Yes.  This is to be expected (as I said, I didn't test the macro, but
this behaviour is obvious now you say it): the footnote number is not
part of the footnote text, but is instead managed automatically by the
(original) \footnote macro.  If you want to use color for the number
too, you need to copy the entire definition of \footnote and modify it
so that it sets the number in color as well the text; or, better yet,
use a more customizable document class like memoir, as was suggested.

	Arthur