Adding Color and Textures to a Model

I'm using Gazebo 9.5.0 and ROS Melodic. I'm following the tutorial [Adding Color and Textures to a Model](http://gazebosim.org/tutorials?tut=color_model#AddingColorandTexturestoaModel) but there are a lot of things wrong. The worst error is that it doesn't mention how to add the textures to the model. I have checked the files in the [repository](https://bitbucket.org/osrf/gazebo_tutorials/src/3d66faff105c9f56a31d3f81ef3932d4071f1c8d/color_model/files/?at=default) to know how to add it. My problem is with the Collada object, [head.dae](https://bitbucket.org/osrf/gazebo_tutorials/raw/default/color_model/files/head.dae) file. If I add the model to a world, the head doesn't appear. From [model.sdf](https://bitbucket.org/osrf/gazebo_tutorials/raw/default/color_model/files/model.sdf), the part that shows the head is: 0 0 0.25 0 0 -2.5model://example_model/meshes/head.dae0.25 0.25 0.25 I thought that the problem is with the uri, but I can see the model in Gazebo editor, and it shows body's material. Maybe something has changed in the latest version of Gazebo and now, this model doesn't work. What's wrong?