Ah...per IPMS Stockholm
"Dark Dull Green
Dull Dark Green was an outgrowth of Bronze Green introduced in September 1942. When introduced, Dull Dark Green was intended as a substitute/replacement for Bronze Green. There has been much confusion about the difference between the two colours. Without being conclusive, it would appear that the shades were very similar, with Bronze Green being slightly darker and semi-gloss. The sheen of Bronze Green was one reason why the all-matt alternative was sought.
When issued, the Dull Dark Green was to be used for tactical aircraft with enclosed crew cabin