HI Jon,
I agree that littleCMS does matter, I just meant for the purpose of outputting separations.
Thanks for your insightful links, as usual I am totally impressed with the work of Inkscape community and your input here is clearly very important. The concept of common swatch library format across different programs is really fantastic, and the kind of co-operation that is needed to provide viable alternatives to adobe creative suite.
Sorry if my tone was too strong, but I have many reasons to prefer working in inkscape, and this particular point is a terrible difficulty in terms of being able to use my artwork over the full range of media.
I'll be looking into your workaround mentioned when I have time!
cheers Mat
LittleCMS doesn't matter particularly as the answer to the original question from Terry Brown. Printing as SPOT colour, means output separations for named colours individually, not mixed as CMYK, RGB, LAB or anything else.
LittleCMS actually does matter.
It gives support for *previewing* output results, for detecting out of gamut colors, and even for using named color icc profiles. The latter is probably the primary way to reliably and portably denote spot colors, but SVG hasn't integrated direct use of them yet.
A functional work-around would be to have an icc profile with a single number input, and that does an effective index into a set of spot colors. A bit strange, but should work with Inkscape 0.46 as it was released.