hexapod_robot/description/urdf/hexapod_robot_materials.xacro

<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro">

  <material name="black">
      <color rgba="0 0 0 1"/>
  </material>

  <material name="blue">
      <color rgba="0 0 1 1"/>
  </material>

  <material name="green">
      <color rgba="0 1 0 1"/>
  </material>

  <material name="red">
      <color rgba="1 0 0 1"/>
  </material>

  <material name="cyan">
      <color rgba="1 0 1 1"/>
  </material>


</robot>