The Jak Connolly “Polymath” series was inspired by his love for oil painting and from the old masters' techniques of the renaissance period.
Often the masters create a monochrome “dead layer” first in a neutral value scale by mixing complementary colors ultra marine (blue) and burnt umber (orange, brown). This would give a very neutral black if mixed correctly.
Polymath value washes are neutral bloq cut down with a hint of white to bring the washes into a true monochrome semi-opacity. Which in turn crafts a smooth transition of values from skin tone to black.
The Polymath series by Jak Connolly is knowledge from the old artists.
Keep in mind that individual perceptions of color may vary based on factors such as screen calibration and lighting conditions.