Labels are the quickest ways to mark a reference to indicate whatever you want. Citavi offers two types of labels. You could use the red label to mean "important" and the blue label to mean "excellent".
Citavi offers you red and blue labels for grouping items.
You can use labels to facilitate the handling of multiple references. For example, to create a selection of references you want to export, you could mark the references with a blue label.
Table view is the fastest way to set labels to multiple references. First, select the references you want to set labels for. Then, on the Edit menu, point to Blue label, and then click Set blue label for selected references or Set red label for selected references, respectively. You will also see other options for clearing labels from the selected references, or clearing labels from all references.