Comment 2 for bug 170366

I think the right way to do CYMK and possibly spot colors is
to implement support for ICC color profiles. They're part
of the SVG standard, and use would basically look something
like this:

  fill:#ff0000 icc-color(genericCYMK, 1.0, 1.0, 0.0, 0.0);

i.e. after the normal color specification, SVG permits an
icc-color() which can specify a color in an arbitrary ICC
color profile. This works pretty much anywhere in SVG that
you can specify a color.

The catch is that you can't really just say "CYMK" any more
than you can "RGB" -- there are many CYMK color profiles,
just as there are many RGB color profiles (at least for RGB,
SVG specifically specifies sRGB). I don't know what a good
real standard CYMK color profile ("genericCYMK" is just a
placeholder) would be.

We might also be able to cope with spot colors in that way,
giving each spot color its own ICC profile or something.
Not sure what the best course of action there would be.

In any case, note also that the as yet unfinalized SVG 1.2
is expected to have some additional support for CYMK and
spot colors, but I've not had time to look into the
specifics yet.