Given the muddle in the literature, I was obliged to hedge my remarks.
In the preface to
The Messerschmitt Bf 110 in Color Profile 1939-1945, Vasco and Estanislau say that
"During the middle of 1941, culminating in an official instruction in November, new colours for the camouflage started to appear. The lighter and greyish RLM 74 and 75 would replace the previous dark greenish colours. For the undersides, a lighter RLM 76 blue would replace the previous RLM 65. However, it is not uncommon to clearly see both camouflages on different aircraft together in the same photograph. As a result, especially during this period, many times it was impossible to distinguish which of the two colour combinations the aircraft was painted in."
They then describe the 2N+AP, based on a photograph of the downed aircraft dated August 16, 1940 on which I based my skin, as follows: "The lighter colour on the fuselage sides, becoming more prevalent on a lot of Bf 110s as the Battle of Britain progressed, is evident on this machine."
Breffort and Jouineau (
Me 110 from 1939 to 1945) embrace the same seeming contradiction. In a discussion of Bf-110 camouflage they say that
"It was at the beginning of 1941 that a new type of camouflage (the so-called 'type 5') appeared on the Luftwaffe's daytime fighters consisting of three shades of grey (RLM 74 Dunkelgrau, RLM 75 Mittelgrau on the upper surfaces and RLM 76 Lichtgrau underneath), with more or less dense patches (RLM 74, 75 or 02) often being added on the fuselage sides and the fins. These three colours were painted according to a single scheme and as with the previous one, comprised dark (RLM 74) sharp-angled patches on a middle grey (RLM 75) background."
But they, too, illustrate the same 2N+AP (which is why it always is better to have at least two examples before skinning) for "summer 1940." Another Bf-110 from July 1940 "sports the later type of camouflage which appeared on the Bf 110s during the Battle of Britain, and was made up of three shades of grey (RLM 74, 75 and 76) with the sides covered in more or less dense patches."
Here, then, we have the new scheme of RLM 74, 75, and 76 being introduced either at the beginning (as you say) or the middle of 1941 but illustrations showing these colors in use by the summer of 1940, which is why I used the phrase "by 1941."