Hi BobK,
Thank you for your unimpeachable explanation and extraordinary further information referring non-standard usage, as well as for your elucidation of the subtle difference between the both usages respectively for "explanation of purpose" and "expression of purpose".
When I see pink color I recall in my mind the imagination of " the pink elephant".
The themas "The pink elephant" has a little philosophical charge.
I have heart "pink elephant" in two separate context.
In the first context the animated character Dumlo (from he Disney movie) saw pink elephant he got drunk. Seeing pink elephant is a euphemism fo drunken hallucination caused by delirium tremens (An acute, sometimes fatal episode of delirium usually caused by withdrawal or abstinence from alcohol following habitual excessive drinking. It also may occur during an episode of heavy alcohol consumption)
Jack London, describing one sort of character used also this term as in: who sees in the extremity of his ecstasy blue mice and pink elephants; He is the type that gives rise to the jokes, in the funny papers.
In the second context the term "pink elephant" was used to describe something obviously that nobody wants to talk aloud.
In business communication when things are going in the wrong direction and the cause is embarrassing or uncomfortable, it can be very difficult to be the first person to speak up. In those cases, when everyone know that there is a problem but nobody will speak about it. He probably might be called 'A pink elephant in the room". Someone trying to raise the topic might say. "Now, let's talk about the big pink elephant that everybody know about and fix this before it gets any worse!"
It is your turn now Bob. You have to ponder a little over my words.
Maybe you are this person who have saw the problem and might wanted to
to raise the topic using the pink color.
V.
Infinitive of purpose 
I don't know what made me choose that colour.]
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