Why grey, you may well ask....
It's an example of 'jointery' making optimal use of the UK's defence resources.
When John Major was PM, his office decided that rationalisation was needed and turned to him for leadership...
"Grey. I like grey. Grey is good. Pass me the peas please, Norma. Grey. Oh yes, absolutely. Have we got any grey?"
Now many year ago, long before WEBF was making noises about Sea Harriers (or even any noises at all as he hadn't been conceived then - in fact, neither had his father), it was RN tradition to paint everything and anything a fetching tone of battleship grey. So the Great Lord Pusser ordered lots of paint. Millions and millions of tins of the stuff. But then along came defence cuts and there was soon more paint than ships.
But Pusser was a wily cove. "Mr Major - I have a solution. You can paint the RAF's aeroplanes with some of my nice grey paint. I've got plenty to spare. You won't need to paint them in two-shades-of-sh*t, shiny white, hemp, brown or anything else. Just grey, lovely grey!"
"Thank you - I shall see that it is done"
And lo, it was.
Except for the trainers. They used the black paint which Pusser had left over from the bit below the waterline of his old battleships. But there wasn't quite enough left in Pusser's paint locker, so the Dominie was painted to look like a skunk, with some of Pusser's finest white flagpole-paint on the top of the fuselage.
But Pusser's paint was too heavy for the wretched little plastic planes which the RAF turned to for elementary flying training when they could no longer afford to buy their own, so they are au naturel in Bundesweiss fibreglass...
Even the Army Air Corps were given the wretched grey, some years after their original supply of green and black became unavailable...
One fine day when Woopert and Wodney of the Umpty-Umpth Queen's Own Chinless Pwancers were discussing horses' fetlocks, the price of bwown bwogues and pink corduroys over afternoon tea, they were alarmed to receive a call from their Corporal-of-Horse.
"Sirs - there's something very strange just arrived at the Q-stores"
W&W decided to investigate. Asking a passing competent NCO to show them the way, they discovered a puzzled quartermaster looking at a large metal object..
"Eh seh, wot is that, Quartermaster?" asked Woopert.
"Errm, it says 'tank' on the label, sir"
"Good gwief! It's not for us, is it? Does it eat hay?" squeaked Wodney.
"Err, it is sir. It seems that we're to be a mechanised cavalry regiment - and this will replace our chargers"
"Menc..Mechan....Mechanised cavalwy? Surely not - it's just isn't done" shrilled Woopert.
But it was true. So some weeks later, vast quantities cans arrived at the Q-stores, marked 'Paint, green, little tanks for the painting of'. Much to the horrified astonishment of the Comptroller General of the Queens Paint. "How simply fwightful. It's sooo not us. I have all these tins of black enamel for making Dobbin's hooves look all spiffing on pawade - I don't want all this wuddy gween!"
But the Corporal-of-Horse, being an NCO with a sound eye for a quick bob or two had an idea. "Errm, excuse me, Sirs, but I fink I can shift a few of them cans. I know a mate in the Army Air Corps...."
"Army Air Corps - wot's that?" enquired Wodney.
"Errm, well, Sir -you know, the chaps who fly around Salisbury Plain in helicopters"
"Oh those fwightful bounders? Rotters who scared m'pony during m'last chukka at Tidders last week. Righty-ho, Corporal-of-Horse, they can have as much as they wuddy well want" said Wodney.
"Errm, my mate'll need a bung to take 'em of me hands, Sir. Perhaps the regimental fund...."
"Certainly, Corporal-of-Horse. The wedgiment's officers will sort that out for you. A couple of thousand or so to help with your efforts?"
"Thank you very much, Sirs, I shall get on to it immediately"
"Well see you do. Now cut along like a good chap. Spot of tiffin, Woopert?"
And not long afterwards, the Army Air Corps' helicopters started to receive nice new green and black paintwork.....until the good Corporal of Horse was nicked by the Redcaps - and Pusser found himself with a new customer.