Hemp was good for large aircraft parked on concrete aprons at ISK, Marham, St. Mawgan, Brize, etc...but only for the naked eye. Trouble is ISK also had a hangar painted brightly in the 80s so you could see for it miles, giving the game away should you have wished to fly your BACKFIRE 'feet dry' instead of fire some ungentlemanly stand-off weapon.
As always the US led, and still lead, the way on camo to defeat sensors of various kinds, including Mk.1 eyeball and IR. Greys provided a middle ground solution to the 'whilst airborne' and 'while on the ground' problem of hiding a plane as best you can. Squadron and national markings were also much reduced in size and sometimes colour due to the IR signature of the decal once applied out of the large water dish and onto the airframe. Look at the daft finishes on F-22 and F-35 now to see what's coming our way in a few short years....unless the F-35 is cancelled of course
Until you've heard a Sidewinder growl in your ears as a SAC stood with a lit match just a few feet in front of the aircraft in a non-official demo test, you'd think all this IR stuff was make believe!