Jessica, you have a knack for identifying relevant topics in plastic sailing ship models.
When a ship was coppered, she pretty much looked like what you have there. Coppering was a very expensive process. It probably started in the late 18th Century and was replaced by the late 19th Century with better performing techniques such as Muntz metal.
By the early 20th Century big ships were no longer built of wood.
The Bounty only was coppered when she was bought by the Royal Navy in 1787. Three years later she was destroyed, so a single coppering was all she had.
She most probably was never careened, certainly not drydocked, or otherwise scraped.
In other words, from the moment she was coppered until the time she was wrecked and burned, the marine growth was unimpeded.
IF she had ever been exposed to air after being coppered, and depending on how long after that, she could have turned green, but she probably stayed in the water, So it would have been a steady progression of barnacles, slime and vegetation.
She spent quite a while in Tubuai at anchor. That probably was a time where she got quite mossy.
Here is my suggestion. Copper gets a patina when exposed to air. And that takes a long time, maybe ten years. In the meanwhile, it goes from copper to brown to black to green.
A ship hauled out usually looks, and smells, just nasty.
So when building a full hull sailing ship model, there's the question of presentation versus reality.
If bright copper, that would be generally accurate for the day she was launched, and appealing.
If covered in marine growth, ugly.
Otherwise the modeler makes an attempt to make the ship look aged, but still attractive.