(Color Names): Add pointer to the X docs about RGB

color specifications.  Improve indexing
(Text Terminal Colors): Replace the description of RGB values by
an xref to "Color Names".

diff --git a/lispref/frames.texi b/lispref/frames.texi
index a33c5b356be3b9d5abb33e8a7d438a817103bbbb..f50be70f473d27cae777e07a7e6a0d0632de1b37 100644 (file)
--- a/lispref/frames.texi
+++ b/lispref/frames.texi
@@ -1588,6 +1588,9 @@ but @code{t} on MS-Windows.
 @node Color Names
 @section Color Names
 
+@cindex color names
+@cindex specify color
+@cindex numerical RGB color specification
   A color name is text (usually in a string) that specifies a color.
 Symbolic names such as @samp{black}, @samp{white}, @samp{red}, etc.,
 are allowed; use @kbd{M-x list-colors-display} to see a list of
@@ -1597,7 +1600,9 @@ as @samp{#@var{rgb}} and @samp{RGB:@var{r}/@var{g}/@var{b}}, where
 and @var{b} specifies the blue level.  You can use either one, two,
 three, or four hex digits for @var{r}; then you must use the same
 number of hex digits for all @var{g} and @var{b} as well, making
-either 3, 6, 9 or 12 hex digits in all.
+either 3, 6, 9 or 12 hex digits in all.  (See the documentation of the
+X Window System for more details about numerical RGB specification of
+colors.)
 
   These functions provide a way to determine which color names are
 valid, and what they look like.  In some cases, the value depends on the
@@ -1657,12 +1662,14 @@ color name, this function returns @code{nil}.
 
 @defun color-values color &optional frame
 @tindex color-values
+@cindex rgb value
 This function returns a value that describes what @var{color} should
 ideally look like on @var{frame}.  If @var{color} is defined, the
 value is a list of three integers, which give the amount of red, the
 amount of green, and the amount of blue.  Each integer ranges in
 principle from 0 to 65535, but some displays may not use the full
-range.  This kind of three-element list is called an @dfn{rgb value}.
+range.  This three-element list is called the @dfn{rgb values} of the
+color.
 
 If @var{color} is not defined, the value is @code{nil}.
 
@@ -1704,11 +1711,8 @@ standard set of colors and will try to use them automatically.
   The functions described in this section control how terminal colors
 are used by Emacs.
 
-@cindex rgb value
-  Several of these functions use or return @dfn{rgb values}.  An rgb
-value is a list of three integers, which give the amount of red, the
-amount of green, and the amount of blue.  Each integer ranges in
-principle from 0 to 65535, but some displays may not use the full range.  .
+  Several of these functions use or return @dfn{rgb values}, described
+in @ref{Color Names}.
 
   These functions accept a display (either a frame or the name of a
 terminal) as an optional argument.  We hope in the future to make Emacs