If everyone contributes their knowledge this might turn into something useful!

I'll start off with Heer: (would be best to keep all branches separate to avoid confusion, keep the others to another thread please)
Pre-war: (35-38)
Models used:
M16
M18
M35
Paint used:
Erbsengrün (mostly seen on M16/18's and other trannies)
Apfelgrün (6003?) normally on M35's
Both decals worn
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1939:
Same as above
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1940:
Added the M40 model
First use of ral 6006 Feldgrün paint as a standard (correct?)
Removal of National tricolored shield ordered early 1940,
M40's mostly came from the factory with a single decal
M35's seen in their original paint scheme at least until after the may 1940 campaign
-------------------------
1941
Many single decal M40's produced and used, many M35's painted over in "m40" scheme
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1942
Introduced the M42 model
Ral 6006 used
Single Decal on the early production
August 10th: Introduction of the Issue helmtarnnetz (helmet net)
Camouflage helmet colours:
Dunkelgelb: RAL 7028
Olivgrün: RAL 6003
Rotbraun: RAL 8017
All you need for a "normandy camo" helmet.
Hope this starts off.