Which option correctly matches a primary colour with its common effect?

Correct answer: Blue and coolness

Option A is correct because blue is a primary colour in the traditional RYB art model and is commonly associated with a cool, calm effect. Green is secondary, formed from yellow and blue, so option B incorrectly calls it primary. Orange is also secondary and is more often linked with warmth or energy than calmness. Violet is not a primary colour in this model, making option D incorrect.