Variable: gnus-unread-mark
gnus-unread-mark is a customizable variable defined in gnus-sum.el.gz.
Value
32
Documentation
Mark used for unread articles.
Source Code
;; Defined in /usr/src/emacs/lisp/gnus/gnus-sum.el.gz
;; FIXME: Although the custom type is `character' for the following variables,
;; using multibyte characters (Latin-1, UTF-8) doesn't work. -- rs
(defcustom gnus-unread-mark ? ;Whitespace
"Mark used for unread articles."
:group 'gnus-summary-marks
:type 'character)