If it is mold, the green will be fuzzy and may have white to it. It looks like a growth of fuzz, if it is moldy.
I find different types of apple or pear wood will be different in color for bark, some with a slightly more yellow-ish brown color to the bark (again depending on the type of pear wood. I have about four different types of pear trees.) or greyish brown in color, whether dried or not.
Mcintosh apple wood seems to be more a dark reddish brown color in color for bark, whereas the yellow transparent apple tree wood, seems to have more of a greenish brown color to the bark(I've noticed the difference as I have had my pick of different apple trees.). There are other apple trees too, where the bark is slightly different in color.
If you are worried, you can just bake it a bit longer though. Sometimes the wood will be green if it hasn't been baked properly.
If you're talking about the actual wood itself and not just the bark, then it is more than likely it wasn't thoroughly baked and might need to be baked a bit longer.