The Namespace Prefixes command pops up the Namespace Prefixes dialog (screenshot below), which displays all the namespaces in the taxonomy, including those of imported taxonomies. In the Namespace Prefixes dialog you can edit namespaces and prefixes, and set background colors for individual namespaces. When a background color is set for a namespace, elements in that namespaces appear in the Main Window and entry helpers with that background color. Note that a color setting for a given namespace applies for that namespace across all taxonomy documents opened in XBRL View.
To add or delete a namespace, use the Add or Delete buttons, respectively. A color is assigned to a namespace via the color palette for that namespace. When you are done with editing in the Namespaces dialog, click OK to finish.
The target namespace of the taxonomy is also listed in the Namespaces dialog. The target namespace, however, should not be modified in this dialog, but via the Set Target Namespace command. For more information on target namespaces, see the XBRL section of the documentation.