They're for real, all right. They're called 'immersion gloves' and finished off the effect of being enclosed in a waterproof [oh, all right, water-resistant] suit encasing the body from the neck down. The immersion suit had rubber neck and wrist seals and was manufactured in a woven fabric that breathed when dry. When wet, the threads swelled and closed up the weave - very effective it was, too. The feet were encased in waterproof 'socks', glue-welded onto the bottom of the suit legs. It was worn over a one-piece, thick acrylan-pile undersuit [which provided the insulation - the immersion suit was to keep you dry, not warm].
I, too, have only been issued with the green version; however, that's not to say there wasn't a white version - it's quite possible that a white version was manufactured and issued.
WhatLimit is correct in saying that they were essential to keep the fingers and hands working. Cold was the biggest enemy after an over-sea bailout. Hypothermia has killed a significant number of aviators who had successfully abandoned aircraft, and the first period in the water was critical for the individual to get rid of parachute and inflate and get into the dinghy.
Johno617tonka paints a hilarious picture! Now that must be the way to identify the arch-poseur! Immersion gloves on a warm sunny day over the centre of England! I wonder how he [or she] would explain away that one if challenged?