note wiki page "color tables"

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@39111 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.colors/r.colors.html

@@ -281,6 +281,12 @@ r.colors current_raster -n rast=current_raster
 <a href="r.univar.html">r.univar</a>,
 <a href="v.colors.html">v.colors</a>
 </em>
+
+<p>
+See also wiki
+page <a href="http://grass.osgeo.org/wiki/Color_tables">Color
+tables</a> (from GRASS User Wiki)
+
 <p>
 <a href="http://colorbrewer.org">ColorBrewer</a> is an online tool designed to
 help people select good color schemes for maps and other graphics.