code: public static void attachCoordinateAxes(Vector3f pos, float size, AssetManager assetManager, Node rootNode) {
          Arrow arrow = new Arrow(Vector3f.UNIT_X.mult(size));
          arrow.setLineWidth(4); // make arrow thicker
          putShape(arrow, ColorRGBA.Green, assetManager, rootNode).setLocalTranslation(pos);
  
          arrow = new Arrow(Vector3f.UNIT_Y.mult(size));
          arrow.setLineWidth(4); // make arrow thicker
          putShape(arrow, ColorRGBA.Blue, assetManager, rootNode).setLocalTranslation(pos);
  
          arrow = new Arrow(Vector3f.UNIT_Z.mult(size));
          arrow.setLineWidth(4); // make arrow thicker
          putShape(arrow, ColorRGBA.Red, assetManager, rootNode).setLocalTranslation(pos);
      }
docs: Code based on http://jmonkeyengine.org/wiki/doku.php/jme3:advanced:debugging