Comment 10 for bug 166622

What a heck, confirmed!!

The way to circumvent is rather simple. Store the object the color corresponds to. If the object is the same and current HSL/CMYK color maps to the same RGB color, change nothing.

But the problem is more fundamental. Inkscape uses SVG as internal format. In some aspects, Lack of CMYK colors if rather restrictive for those who design for paper. After some time, you'll end up with two separate formats: Inkscape internal (for example, *.ink) and W3c export (*.svg).