Your icon should primarily use the eight static grays with the eight static colors used mostly as accents. The eight static colors are very strong and can easily be overused. Using mostly the static grays allows icons to blend gracefully with the already colorful desktop environment. The static colors can be dithered with the static grays to tone the colors down for coverage of larger areas. The grays can also be used to smooth the edges of icons, this is sometimes referred to as "anti-aliasing".
It is recommended not to use the dynamic colors in File Manager icons, because the appearance of the icon will change when the user changes color palettes. Such a change could be inappropriate as well as unpredictably ugly.