I am not sure what you are seeing but here are two possibilities. First, green and brown are natural colors for a camphor tree's trunk. It could be normal bark growth. Second there are things that live on bark like mosses and lichens. These don't harm the tree and can be ignored or scraped off if you wish. If you feel these are not the things you are seeing try taking a sample to your County Extension Office for them to look at and diagnose for you. They should be able to identify the stuff with a sample in hand.
Thanks for the question. Please stop in again soon!
Q&A Library Searching Tips