2 x summary buffer line color

[Emanuel Berg]

1) I'd like a line in the summary buffer only to tell author and
subject, but I'd like those elements to be in different colors.

This is how far I got (in .gnus):

(setq gnus-summary-line-format "%U%R%I%a: %s\n")

Is there a markup for colors?

2) How do you define your own highlighting as for read and unread
articles? Again, I added this to .gnus, but it fell short because I
don't know how to define those last elements of the association list
element (they are not Emacs variables, and not Emacs functions, and
those are the only things I know how to track (with C-h v and C-h f,
respectively)).

(setq gnus-summary-highlight
      '(((eq mark gnus-unread-mark) . gnus-summary-normal-unread)
        (t . gnus-summary-normal-read) ))

Thank you :)
-- 
Emanuel Berg - programmer (hire me!)
CV + code + screenshots: http://user.it.uu.se/~embe8573