Paul,
I think I just found the answer about your Lysander and how they were painted ...
This photo came from the Imperial War Museum, and reportedly shows a Lizzie with the following caption:
"Royal Air Force in France, 1939-1940.
Lysander Mark II, L4767 ‘OO-E’, of No. 13 Squadron RAF, on the ground at Mons-en-Chaussee, France, as ground crew investigate a deflated tyre on the port undercarriage. The serial number has been painted over for security purposes. Date between 1939 and 1940"
This plane looks as if it too has the entire fuselage painted with brown and green, just as your decal sheet has it depicted...
The lighter color under the wings and stabilizer could very well be "Aluminum Dope". If you look at the next picture it becomes even more apparent, since the wing that's visible on the first plane photo of "KJ-M" and "KJ-O" is dark probably in the RAF "night" color.
It looks as if the planes from "No. 16 Squadron" were also painted in this manner, with the brown and green fuselage colors extending all the way around.
Number 16 Squadron flew alongside Number 4 Squadron, over Northern France in 1939 / 1940.
No. 16 SQ had the fuselage side codes of "K J".
I also managed to find a good photo of a few "Number 16 Squadron" Lysander's in flight.
(You just have to love the internet... What did we do back in the day before it's existence ? We either purchased a lot of books or spent some serious time in the library...)
These planes appear to have the fuselages painted in green and brown as well.
However, they also look as if the underwing surfaces were white on one side and black on the other. If you look really close, the ailerons are a much lighter color on the dark wing, and darker on the light wing, as if the ailerons were painted in opposite colors of the wings.
But then if you look at the nose of "OO - E" it is different...
It has the same pattern as "KJ - L" in the second photo...
Maybe the rudder and fin were replaced on "OO - E" since the fuselage is painted like "KJ - L " ?
If you look close at "OO-E" from the first photo, then compare it to the second two planes in the last picture (KJ - M and KJ - O), you will see they demarcation lines between the colors looks almost identical. The only difference I noticed is the colors seem to be reveres on the "OO - E" plane, with the green and brown switched in positions...
I also am posting a link to another website that is dedicated the 4th Squadron. This link should take you right to the unit losses during the time frame that your plane would have served. It lists the crew members names, sometimes the aircraft serial number and if you are very lucky, once in a while the fuselage side codes are also listed.
Here's the link:
http://www.epibreren.com/ww2/raf/4_squadron.html
Hope this helps on your venture my friend...
Now I'm back to masking a certain Heinkel...