FrameMaker uses the Windows GDI for printing color to PostScript. Thus, FrameMaker in Windows is limited to the RGB output permitted by every Windows OS.
EPS-format graphics maintain CMYK values and are unaffected by Windows.
Thus, to pass CMYK color to PS print files from FrameMaker in Windows, use EPS graphics.
Other than that, you need a third-party color utility that will support your need to get CMYK out of the Microsoft Windows environment.
ColourChameleon lets you remap the RGB colours in the postscript output
to Pantone Spot or to CMYK as you require. It then makes the PDF with
the correct colours.