When color is the most important issue

Cyan, magenta, yellow and black are four process colors used for printing. CMYK color mode is very different from RGB from the point of displaying colors. Colors displayed on your monitor in RGB may not be printable in the gamut range of your CMYK printer, and vice versa, your CMYK images can be incorrectly represented on the web. In order for CMYK colors to display with a reasonable RGB simulation on the screen you will need appropriate conversion. Example on how you can do it with ImageConverter Plus is here:
ICPCL.exe -convertto tiff bpp:24 dither:no -source “C:Source Imagescmyk.tif” -dest “C:out” -oper ColorProfile profile_path:”C:WINDOWSsystem32spooldriverscolorPhotoshop4DefaultCMYK.icc”

Note that the conversion of a CMYK color to RGB, followed by the reverse conversion (that is from RGB to CMYK) may not result in the original CMYK color. Therefore, ideally, these conversions must not be used in any process where color matching is critical.