John, most of the reading I've done on the La's and LaGGs point out that the Russians were realists, with a shortage of aluminum to use to build fighters with, at least until the Lend-Lease program got running up to steam, but they had lots of wood. Much of their fighter aircraft only lasted a month or so in the field, so even using any kind of preservative was not usually done.
I'm not certain how much wood was used in wing construction beyond the spar and ribs. Most likely they were skinned with some type of plywood. If you can get a picture of the inside of the gear wells, I'd almost bet that the colors used are basically the same as the outside.
This lack of preservatives has been the reason few WWll Russian fighters have survived.