Ok so I'll come back to my initial problem which is compatibility with the SVG format : When I export a path colored in CMYK (0,0,0,100) and open the SVG file, it comes back as CMYK (68,67,65,74) => is this possible to save CMYK values in the SVG Format ?
It causes problems of compatibility with other softwares such as inkscape which do not have the same conversion formula (with inkscape, RGB (0, 0, 0) is CMYK (0,0,0,100)). So, often, when people share works made with Inkscape, we have to check every black path to put it back to (0,0,0,100) so as for it to be printed with black ink only, which is quite time consuming...