Hi BMG50,
I have a beginning of answer to your question.
Denominations are original ones in French.
- Boulet ogival Mle 1916 : no painting, no markings
- Boulet ogival Mle 1935 : no painting, no markings
- Obus porte-message type BLM (Bourguignon,Laroze, Moulins) : painting red on cylinder part of shell, blue on ogival part. Marking black on body (loading manufacturer, day of loading, and marking PM)
- Obus explosif Mle 1916 (fuzing Robin 1916, Gaba 1918 or RSA 1933) : painting body Yellow
- Obus explosif Mle 1917 : painting white between the two rotating bands and 4 cm above upper band, rest of the shell grey-blue
In all cases, the part under the rotating bands (part of the shell that fits into the case) receives a layer of lacquer.
That's all what I have about the marking of French 37 mm.
Yoda