Some of us are devoid of, or lacking in, nature's own 'head covering' and find these warmer and more comfortable. As I wear mine often, and have to pay for it out of my own pocket, I don't see why I shouldn't have one that is comfortable ... if that's alright with you Dried Plum? The red-lined ones to which you refer are apparently what E C Snaith provide 'off-the-shelf'.
I do not possess a flying overall - though your point is well made. Don't the buttons and badges on a chip bag present a FOD hazard?
As for different colours, simply a means to distinguish between one's own and the other hats, and discourage 'borrowers'.
What is 'M T V' ? I can't find any reference to it in the JSP101!
STH