If a little yellow is added to orange, in which direction will the colour shift?

Correct answer: Yellow-orange

Adding a small amount of yellow to orange shifts the hue toward yellow, producing yellow-orange; therefore option C is correct. Orange and yellow are neighbouring warm colours on the colour wheel, so the change is gradual rather than a move toward an unrelated hue. Red-orange would result if red were added to orange. The direction of a mixture generally follows the colour that has been added.