Function: _def_graphcolormap
Class: default
Section: default
C-Name: sd_graphcolormap
Prototype:
Help:
Doc: a vector of colors, to be used by hi-res graphing routines. Its length is
 arbitrary, but it must contain at least 3 entries: the first 3 colors are
 used for background, frame/ticks and axes respectively. All colors in the
 colormap may be freely used in \tet{plotcolor} calls.

 A color is either given as in the default by character strings or by an RGB
 code. For valid color names, see the standard \kbd{rgb.txt} file in X11
 distributions, where we restrict to lowercase letters and remove all
 whitespace from color names. An RGB code is a vector with 3 integer entries
 between 0 and 255 or a \kbd{\#} followed by 6 hexadecimal digits.
 For instance \kbd{[250, 235, 215]}, \kbd{"\#faebd7"}  and
 \kbd{"antiquewhite"} all represent the same color.

 The default value is [\kbd{"white"}, \kbd{"black"}, \kbd{"blue"},
 \kbd{"violetred"}, \kbd{"red"}, \kbd{"green"}, \kbd{"grey"},
 \kbd{"gainsboro"}].

 The colormap elements can not be changed individually as in a vector (you must
 either leave the colormap alone or change it globally). All color functions
 allow you either to hardcode a color given its descriptive name or RGB code,
 or to use a relative color scheme by changing the colormap and referring to an
 index in that table: for historical and compatibility reasons,
 the indexing is $0$-based (as in C) and not $1$-based as would be expected in
 a GP vector. This means that the index~$0$ in the default colormap represents
 \kbd{"white"}, $1$ is \kbd{"black"}, and so on.
