The ones I know are completely brown.
They put their four front legs together, two by two, and sort of point at you.
I was told that they are aggressive because they are well fed because they feed on the sap from the bananas whereas most spiders are usually hungry.
Wandering spiders do not feed on banana sap. They hunt small invertebrates on the forest floor at night and hide among bananas, or other dark and protected locations during the day. The defensive posture you described is one way to help identify them.