Labels in Mac OS are a type of seven distinct, colored parameters of metadata that can be attributed to files, folders and disks in the operating system. The labels were introduced in System 7 and were kept until the release of Mac OS 9. Mac OS X versions 10.0, 10.1 and 10.2 lacked the attribute, which was reintroduced in Mac OS X version 10.3, though not without criticism.
The labels in Mac OS X let the user give colored backgrounds to System items in three different types of views, through the action menu applicable to the selected icon.
In the older pre-Mac OS X versions the choice of a color would cause the icon to completely wash itself out in that color, losing some distinct traits in the process. The new label feature here applies color only to the background of file names. When a labeled item is selected in Mac OS X column view, a colored dot after the name indicates the label.
There is a choice of seven colors, which cannot easily be exchanged for other colors. The names of the colors however can be changed at will, to represent categories assigned to the label colors (both label colors and names can be customized in pre-OS X systems, however; Mac OS 8 and 9 provided this functionality through the Labels tab in the Finder Preferences dialog, while System 7 provided a separate Labels control panel). Labels in OS 9 and earlier were specific to an individual install; Booting into another install, be it on another Mac or different disk would show different colors and names unless set identically.