Flagging results gives you the ability to mark a document with a colored flag that is stored until the flag is removed, including when Perceptive Enterprise Search - Local Administration Console is closed or the machine is rebooted.
Perceptive Search allow for up to six different flag colors, which you can rename to suit your needs. By default the flags are named after their color of Blue, Yellow, Red, Green, Purple and Brown.
To customize your flags:
Select Tools > Preferences and select Document Flagging.
Each flag color can be given its own name, the name will be shown in the flagging menus.
Flag maintenance can be run on the flag database to recover space and remove deleted documents.