There will be no color conversion if the original image does not contain an image profile. I have updated the documentation to explain this better. You should do the following:
using (MagickImage image = new MagickImage("meat.jpg")) { image.AddProfile(ColorProfile.USWebCoatedSWOP); // Or another CMYK profile image.AddProfile(ColorProfile.SRGB); image.ColorSpace = ColorSpace.sRGB; image.Write("meat.rgb.jpg"); }