Exposed flap/wing structure on 1/48 Gnat - colour?

[MajorClanger]

I'm building the Airfix 1/48 Gnat, to be painted up in the Yellowjacks scheme. I chose to build with flaps down, but the instructions are silent as to how to paint the exposed portions of the wing interior and flaps (see picture).

I've searched online but haven't been able to find any good photos of Gnats showing this area. Looking at other Gnat model builds I've seen this done variously as bare metal, white/grey or the same colour as the rest of the flaps.

Any suggestions as for the right colour (or colours if the wing and flap portions should be different) for Gnats in general and the Yellowjacks scheme in particular?

[Mark]

There is this photo http://cdn-www.airliners.net/aviation-photos/photos/3/6/4/0999463.jpg which is copyright Alistair Bridges on Airliners.net that shows the hidden upper surface of the lowered flap to be yellow.

Sorry if I broke protocol by posting that link.

[canberra kid]

I know it's not a yellow jacks Gnat but looking through all my photos they would suggest it was the same colour as the wing

John

[MajorClanger]

Thanks both - very helpful! Yellow it is then...