Which colour can be used in a tiny amount instead of black to create a natural dark blue in poster colour?

Correct answer: Orange

The governing concept is complementary colour mixing and controlled neutralisation. Orange lies opposite blue in the colour wheel, so a very small amount can reduce blue’s excessive brightness and make it appear deeper and more natural. Option A is therefore correct. White raises lightness, yellow shifts the hue toward green, and light green usually makes the mixture lighter or more greenish rather than naturally dark blue. Too much orange may produce a muddy or brown result.