CMYK color with rgb-icc() and cmyk()
Here is an example of drawing CMYK color by specifying rgb-icc(<R>,<G>,<B>,#CMYK,<C>,<M>,<Y>,<K>). Specify 0.0–1.0 or % value in CMYK value. cmyk(<C>,<M>,<Y>,<K>) is equivalent to rgb-icc(#CMYK,<C>,<M>,<Y>,<K>).
The following formulas are used for RGB calculation:

Red = 1 - minimum(1, Cyan X (1 - Black) + Black)

Green = 1 - minimum(1, Magenta X (1 - Black) + Black)

Blue = 1 - minimum(1, Yellow X (1 - Black) + Black)

rgb-icc(164,164,164,#CMYK,0.2, 0.2, 0.2, 0.2) ------------- rgb-icc(64%,64%,48%,#CMYK, 20%, 20%, 40%, 20%)
rgb-icc(123,123,123,#CMYK,0.2, 0.2, 0.2, 0.4) ------------- rgb-icc(48%,48%,48%,#CMYK, 20%, 20%, 20%, 40%)
rgb-icc(164,164,123,#CMYK,0.2, 0.2, 0.4, 0.2) ------------- rgb-icc(64%,64%,48%,#CMYK, 20%, 20%, 40%, 20%)
rgb-icc(164,123,164,#CMYK,0.2, 0.4, 0.2, 0.2) ------------- rgb-icc(64%,48%,64%,#CMYK, 20%, 40%, 20%, 20%)
rgb-icc(123,164,164,#CMYK,0.4, 0.2, 0.2, 0.2) ------------- rgb-icc(48%,64%,64%,#CMYK, 40%, 20%, 20%, 20%)
rgb-icc(123,123,92,#CMYK,0.2, 0.2, 0.4, 0.4) ------------- rgb-icc(48%,48%,36%,#CMYK, 20%, 20%, 40%, 40%)
rgb-icc(164,123,123,#CMYK,0.2, 0.4, 0.4, 0.2) ------------- rgb-icc(64%,48%,48%,#CMYK, 20%, 40%, 40%, 20%)
rgb-icc(123,123,164,#CMYK,0.4, 0.4, 0.2, 0.2) ------------- rgb-icc(48%,48%,64%,#CMYK, 40%, 40%, 20%, 20%)