dvips: Color specifications
7.6.1 Color specifications
--------------------------
What is a color specification? One of three things. First, it might be
a PostScript procedure as defined in a PostScript header file. The
'color.pro' file defines 64 of these, including 'Maroon'. This
PostScript procedure must set the current color to be some value; in
this case, 'Maroon' is defined as '0 0.87 0.68 0.32 setcmykcolor'.
The second possibility is the name of a color model (initially, one
of 'rgb', 'hsb', 'cmyk', or 'gray') followed by the appropriate number
of parameters. When Dvips encounters such a macro, it sends out the
parameters first, followed by the string created by prefixing 'TeXcolor'
to the color model. Thus, the color specification 'rgb 0.3 0.4 0.5'
would generate the PostScript code '0.3 0.4 0.5 TeXrgbcolor'. Note that
the case of zero arguments is disallowed, as that is handled by the
single keyword case ('Maroon') above, where no changes to the name are
made before it is sent to the PostScript file.
The third and final type of color specification is a double quote
followed by any sequence of PostScript. The double quote is stripped
from the output. For instance, the color specification '"AggiePattern
setpattern' will set the 'color' to the Aggie logo pattern (assuming
such exists.)