The Pacific Banana Slug gets its name from its yellow colour but the slug will change its colour depending on the environment, what it has recently eaten and its health. This is the colour we usually see these slugs in our area. These slugs make a crystalline matrix that can absorb 100 times its weight of water. We call this stuff "slime". It's common to see slime trails in our neighbourhood woods.
Photography notes:
The top of the original image has been cropped to remove distractingly shiny pine needles.