I don’t know where you are importing it from, but it kind of doesn’t matter. Unreal Engine has it’s own way of doing materials. As such you need to make or remake your materials in Unreal after importing to get it to look how you probably want it to look. Nothing will import materials perfectly and with all the options available in Unreal.
If everything is green than you might have a filter going on in the post process to give it that green tint.
I also don’t see how this is a skeletal problem. The skeleton has nothing to do with materials on import.