1. Red

 A. Subconjunctival hemorrhage

2. Yellow

 A. Bilirubinemia-obstructive or hemorrhagic jaundice
 B. Picric acid
 C. Leptospirosis
 D. Brucellosis (Barg disease or Mediterranean fever)
 E. Aromatic nitro and amino compounds
 F. Conjunctival fat-occurs primarily in older and black patients
 G. Blood pigment tinge of malaria, blackwater fever, and yellow fever

3. Gray (black)

 *A. Argyrosis (silver)
 B. Drugs, including the following:
atabrine
nitrochlorobenzene
phenols, specifically phenylic acid and carbon disulfide
 C. Chrysiasis (gold)-grayish green effect
 D. Arsenicals-ash white
 E. Mascara

4. Brown

 A. Subconjunctival hemorrhage-fine brown spots
 B. Pigmentary limbal ring associated with senile, traumatic, or diseased conditions
 *C. Benign melanosis-overactivity of melanocytes
  (1) Epithelial-congenital or acquired, following radiation or use of     chemicals (arsenic); in Addison disease (adrenal cortical insufficiency);    because of chronic conjunctivitis (trachoma, vernal conjunctivitis,     onchocerciasis, keratomalacia)
  (2) Subepithelial-congenital or in association with melanosis oculi or    nevus of
 D. Neoplasms
  *(1) Nevus-most common in children, localized, stationary, elevated,    cystic, mayor may not have pigmentation
  *(2) Malignant melanoma arising from preexisting nevus, apparently    normal conjunctiva, or from an area of acquired pigmentation     (intraepithelial melanoma); occurs primarily in middle age; diffuse, flat,    pigmentation; progressive; no cysts
E. Drugs, including the following:
 

aminoquinoline combinations     (benzoquinone, paraquinone,     hydroquinone) aniline dyes bromides

chromic acid and chromates phenol     derivatives phenothiazine sympathomimetics (adrenalin)

 F. Metabolic or vitamin disturbance, including alkaptonuria

5. Blue pigmentation

 A. Ink tattoo from pens
 B. Manganese dust

Crawford JB, et al. Combined nevi of the conjunctiva. Arch Ophthalmol 1999; 117:1121-1127.

Fraunfelder FT, Fraunfelder FW. Drug-induced ocular side effects. Woburn, MA: Butterworth-Heinemann, 2001.

Roy FH. Ocular syndromes and systemic diseases, 3rd ed. Philadelphia: Lippincott Williams & Wilkins, 2002.