Looks like I was beat to the punch, but thank you for the vote of confidence, Svenn:)
I would concur with what's been said so far, and only add that during the early portion of the Second World War, some Japanese Army vehicles were still painted in a shade that is sometimes referred to as "Brown Green" in translated Japanese sources. This is essentially a very brownish green tinge, not unlike that seen in the recolored photo of the Dowa that you found or in the helmet provided by Jim, albeit with a tad red than seen in the recolored photos.
Also, note that the helmet shown by Jim is an -Army- helmet (thus the star). If it were a naval helmet, it would have different insignia, and likely be in a different color, too.
However, I do agree that it seems to have been recolored. If the vehicle is indeed a naval armored car, as is the case, I would lean strongly toward blue-grey.
-Doc