These icons are used by swift-doc to distinguish between different kinds of symbols in documentation. They draw inspiration from Xcode's Symbol Navigator and Minimap (also known as "Code Sense" icons), making changes to better fit their use in swift-doc.

For example, types in Xcode are typically represented with the same color (purple), distinguished only by their first letter (C for classes, S for structures, and so on). In swift-doc, we assign distinct colors for classes, enumerations, protocols, and structures, and apply them consistently throughout the site in icons as well as links and symbol graphs. Note, however, that green is shared by top-level functions, variables, and typealiases, and that properties and cases are both teal, as they're less likely to be displayed alongside one another.