Which option shows a dark shade of a cool colour?

Correct answer: Dark blue

The governing concept is colour temperature combined with value. Blue is generally a cool colour, and making it darker produces a dark shade, often by adding black or reducing its lightness. Thus, dark blue satisfies both conditions in the question. Orange, yellow-orange and red belong to the warm family even when their value or brightness changes. A colour’s shade describes how light or dark it is, while its temperature describes whether it appears warm or cool.