Label (macOS)
In Apple's Macintosh operating systems, labels are a type of seven distinct colored and named parameters of metadata that can be attributed to items in the filesystem. Labels were introduced in Macintosh System 7, released in 1991, and they were an improvement of the ability to colorize items in earlier versions of the Finder. Labels remained a feature of the Macintosh operating system through the end of Mac OS 9 in late 2001, but they were omitted from Mac OS X versions 10.0 to 10.2, before being reintroduced in version 10.3 in 2003, though not without criticism. During the short time period when Mac OS X lacked labels, third-party software replicated the feature.
In classic Mac OS
In classic Mac OS versions 7 through 9, applying a label to an item causes the item's icon to be tinted in that color when using a color computer monitor, and labels can be used as a search and sorting criterion. There is a choice of seven colors because three bits are reserved for the label color:001 through 111, and 000 for no label. The names of the colors can be changed to represent categories assigned to the label colors. Both label colors and names can be customized in the classic Mac OS 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 Mac OS 9 and earlier, once customized, 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. A colorless label could be produced by changing a label's color to black or white.