There are specs for highlighting, and these are shared by all the format
variables. Text inside the ‘%(’ and ‘%)’ specifiers will get
the special mouse-face property set, which means that it will be
highlighted (with gnus-mouse-face) when you put the mouse pointer
over it.
Text inside the ‘%{’ and ‘%}’ specifiers will have their
normal faces set using gnus-face-0, which is bold by
default. If you say ‘%1{’, you’ll get gnus-face-1 instead,
and so on. Create as many faces as you wish. The same goes for the
mouse-face specs—you can say ‘%3(hello%)’ to have
‘hello’ mouse-highlighted with gnus-mouse-face-3.
Text inside the ‘%<<’ and ‘%>>’ specifiers will get the
special balloon-help property set to
gnus-balloon-face-0. If you say ‘%1<<’, you’ll get
gnus-balloon-face-1 and so on. The gnus-balloon-face-*
variables should be either strings or symbols naming functions that
return a string. When the mouse passes over text with this property
set, a balloon window will appear and display the string. Please
refer to Tooltips in The Emacs Manual for more
information on this. (For technical reasons, the guillemets have been
approximated as ‘<<’ and ‘>>’ in this paragraph.)
Here’s an alternative recipe for the group buffer:
;; Create three face types.
(setq gnus-face-1 'bold)
(setq gnus-face-3 'italic)
;; We want the article count to be in
;; a bold and green face. So we create
;; a new face called my-green-bold.
(copy-face 'bold 'my-green-bold)
;; Set the color.
(set-face-foreground 'my-green-bold "ForestGreen")
(setq gnus-face-2 'my-green-bold)
;; Set the new & fancy format.
(setq gnus-group-line-format
"%M%S%3{%5y%}%2[:%] %(%1{%g%}%)\n")
I’m sure you’ll be able to use this scheme to create totally unreadable and extremely vulgar displays. Have fun!
Note that the ‘%(’ specs (and friends) do not make any sense on the mode-line variables.