I think the images of Wick's aircraft are inconclusive as far as the cockpit colour goes. RLM 66 was certainly used in bombers produced by Junkers in the early years of the war and at least by Heinkel pre-war.
It is rare in Messerschmitt's production at this time. It does occurr,Bartels' Bf 109 E-1,shot down in July 1940,clearly has a dark grey cockpit interior but it is a reconditioned airframe as indicated by the F (flugklar) appended to the W.Nr. 6296F. It is possible that the interior was resprayed,post production,as part of that refurbishment.
It is also fitted with the later,heavier framed hood.The frames are in RLM 66,inside and out,standard at this time.Some units may have resprayed the exterior framing in the camouflage colour but noone likes masking canopies,even at 1:1 scale.
There is no hard and fast rule but generally,without good evidence to the contrary,a Bf 109 of this period would have an RLM 02 interior. The factory changeover to RLM 66 interiors didn't happen until the production of the F series had started,leaving the early Fs with RLM 02 interiors too.
Cheers
Steve