How can I list all the terms of a given vocabulary using Views? I just need to list all the terms of the "Colors" vocabulary using the Drupal 7 version of Views. I thought it was simple to do it, but I can't find a way to get it. 

I can't use contextual filters.
You need to build the view from a taxonomy base as shown in this screenshot (I'm showing Tags; you would need to show Colors):