The six colors of hyperlinks embedded in the text indicate different categories of notes:
Green links (Ireland) refer to Irish history, politics, customs, language, humor, religion, mythology, economics, industry, geography, modes of transportation, flora, fauna, and weather.
Orange links (Literature) signal allusions to published texts including poetry, fiction, drama, critical essays, history, philosophy, scripture, theology, science, biography, hagiography, travelogues, and newspapers.
Brown links (Dublin) point to landforms like the river and bay, the built environment such as streets, canals, buildings, bridges, trams, and statues, cultural ephemera such as money, and civic institutions.
Purple links (Performances) indicate notes about songs, operas, oratorios, stage plays, nursery rhymes, speeches, recitations, advertising pitches, prayers, liturgical rites, performative social gestures, and impromptu clowning.
Red links (The Body) encompass anatomy, sexuality, childbirth, eating, drinking, excretion, clothes, personal accessories, disease, death, medicines, poisons, the physiology of emotion, the vagaries of memory, mental illness, and dreams.
Blue links (The Writer) address narrative styles, techniques, revisions, and effects, as well as textual variants, aesthetic theories, and the shaping of real lives into fictional ones.
These categories are arbitrary, and very often the decision to assign a note to one of them must be arbitrary too, since some notes don't fit any category neatly and many might reasonably be placed in two or three. The Sandycove tower, for instance, may be understood as a physical structure in the environs of Dublin, as a remnant of Ireland's military history, or as a symbol evoking narratives in Homeric and Shakespearean literature. In hundreds of such cases, the category that describes the largest amount of the note’s content is used. Sometimes a colored symbol (§,§,§,§,§,§) at the beginning of a paragraph signals a shift to a new kind of content in the middle of a note.