I have a model with several visual elements attached to a single link:

<link name="torso_casing">
  <visual name="torso_casing_collision_0_visual">
    <geometry>
      <box size="0.015 0.015 0.001" />
    </geometry>
    <origin rpy=" 0. -1.73864026  2.55623365" xyz=" 0.05047744 -0.04820401 -0.00116878" />
  </visual>
  <visual name="torso_casing_collision_1_visual">
    <geometry>
      <box size="0.015 0.015 0.001" />
    </geometry>
    <origin rpy=" 0. -1.70902562  3.04146286" xyz=" 0.06012247 -0.01665401 -0.00116878" />
  </visual>
</link>

Is it possible to add unique material to each of those visuals for Gazebo 9 simulation? I am trying to follow online tutorials, but it seems that the following method can apply material only to the first visual in the referenced link:

  <gazebo reference="link1">
    <material>Gazebo/Orange</material>
  </gazebo>