And with that sorted out, we can return to our regular unscheduled Corsair colors discussion. My turn to post some photos.
First is a -1A on the line at Bridgeport.

Underwings in intermediate blue, obviously. Two things to note here though. First, the dark blue wraps around slightly to the lower leading edge. This area is in shadow on a lot of sunlit pics of Corsairs; people are fooled into thinking the wing is all one color because they don't see a demarcation line up higher, where they're expecting it, and the existing one is concealed in shadow. Second, note the nice contrast between the intermediate blue and insignia blue. The dark blue was very close in tonal value to insignia blue, so if the insignia blue appears distinctly darker than the surrounding paint in a photo, you can be sure the surrounding paint is intermediate blue, no matter how dark it looks. The next two shots illustrate these points.

The underwings look pretty dark here. If this shot only showed the port wing, where there's no insignia, some of our friends might say it looks like dark blue. But there's too much tonal difference between the underwing color and the insignia. It's intermediate blue. I expect that if we saw the side with the insignia on the first pic Rob posted, we'd see the same thing.

Factory fresh F4U-1C. Here the underwings look far darker even than the dark sea blue on top. Aha, a clear case of dark blue underwings! But no. Look closely...

There's the demarcation line outboard of the guns, just where it was on the first photo above. Not only that, but even the sheaths around the gun barrels have a demarcation line, with dark blue on top wrapping around the tips, and lighter color below. Intermediate blue wings again! This shows how much difference light and shadow can make when it interacts with paint tone.
Bottom line, photos are darn tricky to interpret. We know that Navy spec called for intermediate blue underwings on the tri-tone scheme. I've yet to see credible evidence that the factory painted them any other way.
August