Which primary colour is generally considered a cool colour?

Correct answer: Blue

The governing concept is warm-and-cool colour classification. Blue is a primary colour commonly associated with water, sky, calmness, depth, and distance, so it is generally classified as cool. Option D is correct. Red and yellow are usually treated as warm primary colours, while orange is warm but is not a primary colour in the traditional school model. The alternatives therefore fail either by temperature group or colour class.