Hey, sure thing. As for the wood bit, that would depend on the type of wood, and how old the wood is. Assuming the wood is dead, it will slowly turn from whatever shade of brown it was when alive to a light gray hue over an extended period of time. I'm not sure how quickly this happens, though, but it takes awhile. If the wood itself is wet and waterlogged, that will darken the hue up some. Furthermore, a wet/humid environment is going to make the wood rot, which will give it a slight green tinge in places (or a LOT of green, if it's covered in moss).
tl;dr
The older it is, the more bleached it will look. Decide your base hue on that (sliding between the initial brown hue and the endpoint whitish gray), then make it darker depending on how wet the wood is, and add some green tinge if the wood is really wet all the time.
tl;dr
The older it is, the more bleached it will look. Decide your base hue on that (sliding between the initial brown hue and the endpoint whitish gray), then make it darker depending on how wet the wood is, and add some green tinge if the wood is really wet all the time.