Question

When all colors are absorbed, you see:

white
yellow
green
black

Answer 1

Light and ink have different properties, so when you mix all lights together, you get white (hence Prism, Pink Floyd’s album cover) and mixing all inks together give you black.

Answer 2

You see black, since none the wavelengths of light are being reflected back into the eye. Light is a prism, and the wavelength that is reflected is the color that you see.