Ziad, Rick:
Thanks for the pointers to MakeColorMap and ScaleToMap.
Now that I understand how this is intended to work, I see that I need to prepare a vertex-to-color table.
ScaleToMap looks like it's the program that can perform a join between a vertex-to-value table and a value-to-color table, so possibly that's what can be used for the job, though presumably any means of performing a table join would work.
Thanks,
Graham