In substitution type of questions, some particular objects are assigned code names. Then a question is asked that is to be answered in the code language.
If air is called green , green is called blue, blue is called sky, sky is called yellow, yellow is called water and water is called pink, then what is the color of clear sky ?
The colour of clear sky is 'blue' and as given, 'blue' is called 'sky'.
So, the colour of clear sky is 'sky'.