Hans wrote:

The problem is in the space in the name; since this name is used all over the place, an internal cleanup will not help, so this is why we have (yes, undocumented, so ... add to the wiki)

\setupcolors[rgb=no,cmyk=no,spot=yes,state=start]

\definecolor[IFSbluebase] [c=1,m=.56,y=0,k=.18]

\doregisterspotcolorname{IFSbluebase}{PANTONE 294CV} ...

Thank you Hans! Works beautifully. I have added a section about spot colours, including this info about mapping them, to the wiki. I hope no-one objects to the British spelling in that section :-) Duncan