Document the new min-colors face attribute.

etc/NEWS

@@ -713,6 +713,13 @@ than 8 colors.  For example, for `xterm', 16-color, 88-color, and
 the extended number of colors, and defines the appropriate entries for
 all of these colors.
 
++++
+*** Emacs now uses the full range of available colors for the default
+faces when running on a color terminal, including 16-, 88-, and
+256-color xterms.  This means that when you run "emacs -nw" on an
+88-color or 256-color xterm, you will see essentially the same face
+colors as on X.
+
 ---
 *** There's a new support for colors on `rxvt' terminal emulator.
 
@@ -1822,6 +1829,13 @@ a match if part of it has a read-only property.
 configuration files.
 
 * Lisp Changes in Emacs 21.4
++++
+** New face attribute `min-colors' can be used to tailor the face color
+to the number of colors supported by a display, and define the
+foreground and background colors accordingly so that they look best on
+a terminal that supports at least this many colors.  This is now the
+preferred method for defining default faces in a way that makes a good
+use of the capabilities of the display.
 
 ** New function 'define-fringe-bitmap' can now be used to change the
 built-in fringe bitmaps, as well as create new fringe bitmaps.