Which colour is associated with both water and sky?

Correct answer: Blue

Blue is commonly associated with both water and the sky, making option D correct. In colour theory, blue is generally classified as a cool colour and can suggest calmness, depth, freshness, and vastness. Red, orange, and yellow are usually warm colours associated with fire, sunlight, energy, or excitement rather than water and sky. The question asks about common visual association, not the colour of every real object.