What is the colour of the wind?

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To answer a question such as this you might need serious scientific research and practical experimentations in order to prove that the wind does infact have a colour.
I am not Einstein, but I can attempt to add thought to what the colour of the wind is to me.

I believe the colour of the wind is the effect it has on you when it is around you, behind you, or in front of you. Ask yourself the question, what does the wind do for you?
If a negative response is generated, associate it with dark, meaningless, dull colours. If a positive reaction is generated, associate it with bright vibrant cheerful colours.