If equal amounts of red and yellow make orange then toward which colour will the mixture shift when the amount of red is doubled?

Correct answer: Red-orange

The governing concept is proportional influence in a two-pigment mixture. Equal red and yellow produce an orange near the balance point. If the red amount is doubled while the yellow amount stays unchanged, red becomes the dominant component, so the hue shifts from balanced orange toward red-orange. It does not move toward yellow-green or blue-violet, which require different hue influences, and unequal red and yellow alone do not automatically produce grey. Therefore A is correct.