Lch is similar to it's cousin Cie-L*ab, except that it's been rearranged in the shape of a sphere which makes it useful for applications like high-end photo editing and retouching images. Read more about it here
Cmy is frequenty associated with color printing, and it's determined by the relation of colors cyan, magenta and yellow. Unlike Rgb, cmy is subtractive, meaning that higher values are associated with darker colors rather than light.
Color conversions performed using the open source ColorMine library.