These four colors appear multiple times throughout House of Leaves, at least once in each narrative: Zampano writes about the colors of the deadbolts; Johnny writes about the colors of tattoo inks ("cinnabar, lemon, celadon, and indigo"); Pelafina mentions the colors of the pills she takes ("madder, azure, celadon, gamboge"); Chad & Daisy draw with "madder and rose [...] Sunday red and indigo [...] celadon [...] heliotrope and gamboge").
The four colors are often taken to be representative of the "four elements:" fire, earth, water and air.
Individually, blue is the color of the word "house," the color of blueprints, and meant to evoke the blue screen effect used in movies as well as hyperlinks. Navidson is particularly linked with the color blue, given he is the owner of the house and his nickname, "Navy." Blue is associated with open spaces, freedom, intuition, imagination, expansiveness, inspiration, and sensitivity. Blue also represents meanings of depth, trust, loyalty, sincerity, wisdom, confidence, royalty, stability, faith, divinity, and intelligence. Blue is the color of the "X" on Navy's letter to Karen. Note that in the images we have of Zampano's writing, the word "house" does not appear in blue and this was likely an invention of Johnny's.
Red is the color of the minotaur and all struck-out passages appearing in The Navidson Record. It makes up part of the compass on the cover of the full color addition and appears directly (as the word "Red" and prominently as a color) in the collages. Red is associated with love, passion, desire, heat, longing, lust, sexuality, sensitivity, romance, joy, strength, leadership, courage, vigor, willpower, rage, blood, anger, danger, malice, wrath, stress, action, vibrance, radiance, and determination. To recover many of the struck passages, Johnny used turpentine, which can give ink a light brown or reddish tint.
Green is the only of these four colors to not appear on the cover of the book. It is linked with Karen Green. Green is associated with life, renewal, nature, and energy, growth, harmony, freshness, safety, fertility, environment, money, finances, banking, ambition, greed, and jealousy. The index cards holding several footnotes were green.
Yellow appears as part of the compass on the front cover. Perhaps linked with Daisy, named after the flower with a yellow center. Yellow is associated with freshness, happiness, positivity, clarity, energy, optimism, enlightenment, remembrance, intellect, honor, loyalty, and joy, cowardice, deceit, caution, sickness, and jealousy. The index cards were held together by yellow rubber bands.