This is the list of common problems.

Emacs 20.7: Some faces are created using copy-face; these faces are
not printed correctly using M-x color-theme-print.  They will have
(nil) in their spec.  M-x customize-face has the same problem.

Example:

(copy-face 'bold 'new-bold)
(color-theme-spec 'bold)
  => (bold ((t (:bold t))))
(color-theme-spec 'new-bold)
  => (new-bold ((t (nil))))

XEmacs 21.1: Some faces are defined using a certain font instead of
of the correct attribute.  They will have (nil) in their spec.
M-x customize-face has the same problem.

Example:

(color-theme-spec 'bold)
  => (bold ((t (nil))))

XEmacs 21.2 and up, Emacs 21: Not compatible with the custom-theme
mode.  It should be easy to transform the color-theme source into
custom-theme source, however.

If you are running XEmacs, then only foreground and background color
of the default face and only the background color of the text-cursor
face will used.  This is due to the fact that these three pieces of
information are stored as frame parameters in Emacs.

If you are running XEmacs, variables cannot have a frame-local
binding.  Therefore, if color-theme-is-global is set to nil, the
variable settings in a color theme are ignored.

Using Emacs and a non-nil value for color-theme-is-global will
install a new color theme for all frames.  Using XEmacs and a non-nil
value for color-theme-is-global will install a new color theme only
on those frames that are not using a local color theme.

If your system does not define the color names used, you will get the
error "undefined color".  See the output of `list-colors-display' for
a list of colors defined on your display.

The :box, :height, and other new attributes will be honored in Emacs
21, but when you print such a color-theme on Emacs 20 or XEmacs 21,
the information will get lost.  So don't do that.  Furthermore,
customizing these faces may end up showing you a lisp expression
instead of the real widgets on Emacs 20 or XEmacs 21 because these
attributes are not understood.

:inverse-video handling differs in Emacs and XEmacs.  We therefore do
away with it.  When printing a color-theme, the inverse-video
attribute should be handled correctly without ever appearing in color
themes.  For maintenance, the following might be usefull for
query-replace-regexp.
:background "\([^"]*\)"\(.*\):foreground "\([^"]*\)"\(.*\) :inverse-video t
:background "\3"\2:foreground "\1"\4

In XEmacs 21.1, some of the face tests don't work.  Example:
(custom-face-bold 'bold) returns nil on my system.  A bug report was
submitted.

Emacs 20 users will loose with new color themes, because these will
set the colors of the default face only, leaving frame background
untouched.  In Emacs 20, the colors of the default face and of the
frame could be changed independently.  In Emacs 21, this is no longer
true.  New color themes will not be made backwards compatible.

This release was superficially tested with Emacs 21.x/22.x and XEmacs 21.4.