What generally results when all three primary pigment colours are mixed in nearly equal amounts?

Correct answer: Dull brown or grey

In subtractive pigment mixing, each pigment absorbs some wavelengths of light. Mixing all three primary pigments in nearly equal amounts therefore absorbs much of the visible light and usually produces a muddy, dull brown or grey. Bright white is associated with reflected light rather than mixed paint, while orange and green require only particular pairs. Hence option B is correct.