What colour shift occurs when a small amount of yellow is added to blue?

Correct answer: Bluish green

The governing concept is colour bias created by unequal proportions. Blue and yellow mix to form green. Since the amount of yellow is small and blue remains the larger component, the resulting green keeps a blue bias and appears bluish green. A reddish orange mixture would require red and yellow, yellowish red would involve red with yellow, and reddish violet would involve red and blue. Therefore, A is the only suitable shift.