The colors tag is a direct child of the tinderbox tag.
<colors>[nested <color> tags or empty]</colors>
The tag takes no attributes and acts as a container for color tags, i.e. a list of defined (named) colours for the current TBX. The list always includes a set of built-in colours. The user may delete or edit these from within the Tinderbox UI as well as save their own new colours.