Post any defects you find in the released or beta versions of the ImageMagick software here. Include the ImageMagick version, OS, and any command-line required to reproduce the problem. Got a patch for a bug? Post it here.
Some operations are performed in the RGB colorspace such as drawing. Here the fill color is auto converted to CMYK. Other operations use fill directly in the CMYK colorspace. Which operation are you performing with the fill color?