Nail Discoloration: What Different Colors Mean for Your

Toenail discoloration is one of the most information-rich physical signs in podiatric medicine. The color—yellow, white, black, brown, green, red, blue, or pale—combined with the pattern, onset, and affected nails narrows the differential diagnosis significantly before any testing is done. Understanding what each color pattern indicates helps you distinguish between benign cosmetic changes and findings that warrant prompt medical attention.

At Balance Foot & Ankle in Howell and Bloomfield Hills, MI, we evaluate nail discoloration with clinical examination, nail culture or PAS histology when fungal infection is suspected, and systemic referral when the nail findings suggest an underlying condition beyond the foot.

Toenail Color Guide: What Each Color Signals

Color	Common Causes	Concerning Causes (Don’t Miss)	Action
Yellow / yellow-brown	Onychomycosis (fungal); nail polish staining; chronic shoe pressure	Yellow nail syndrome (lymphedema + respiratory disease); psoriasis	Nail culture / PAS stain; pulmonology referral if yellow nail syndrome suspected
White (leukonychia)	Trauma (white spots from minor injury); nail polish leaching; fungal (superficial white onychomycosis)	Terry’s nails (liver disease, heart failure, diabetes); Muehrcke’s lines (hypoalbuminemia); Mees’ lines (arsenic poisoning, chemotherapy)	See detailed white nail guide; systemic workup for Terry’s/Muehrcke’s/Mees’ patterns
Black / dark brown	Subungual hematoma (trauma); melanonychia (melanin deposition from benign causes)	Subungual melanoma (Hutchinson’s sign: pigment spreading to nail fold)	Dermoscopy evaluation; biopsy if Hutchinson’s sign or irregular pigmentation
Green	Pseudomonas aeruginosa bacterial infection under nail; chloronychia (swimmer’s nail)	Green nail with significant onycholysis + immune compromise → invasive infection	Topical gentamicin or ciprofloxacin; let nail dry; trim onycholytic portion
Red / dark red	Subungual hematoma (most common); splinter hemorrhages under nail	Splinter hemorrhages → infective endocarditis; vasculitis; trichinosis	Cardiac workup if multiple splinter hemorrhages + systemic symptoms
Blue / purple	Subungual hematoma (acute); cyanosis from cold or vasoconstriction	Systemic hypoxia (COPD, heart failure); Wilson’s disease; antimalarial medication	Pulse oximetry; cardiorespiratory evaluation if persistent
Pale / washed out	Anemia; poor nail bed perfusion	Terry’s nails (liver cirrhosis); Lindsay’s nails (renal failure: half and half nails)	CBC; liver function; renal function panel
Brown / tan streaks	Melanonychia striata (normal in darker-skinned individuals); trauma; medications (hydroxyurea, minocycline)	Subungual melanoma (variable width streak, Hutchinson’s sign, adult-onset single nail)	Dermatology / podiatry evaluation; biopsy criteria apply

Melanonychia: When Brown Streaks Need Evaluation

Melanonychia (brown/black longitudinal streaks in the nail) is one of the most important findings to evaluate accurately. In individuals with darker skin tones (Fitzpatrick types IV–VI), single or multiple brown streaks are normal and represent benign melanocyte activation—no action is needed. In lighter-skinned individuals, new adult-onset single-nail melanonychia requires dermoscopic evaluation and possible nail matrix biopsy to exclude subungual melanoma.

Hutchinson’s sign—pigmentation spreading from the nail bed onto the proximal or lateral nail folds—is a specific sign of subungual melanoma and requires urgent biopsy regardless of skin tone. Any streak that is widening over time, has irregular borders, or occupies more than 2/3 of the nail width warrants biopsy. Subungual melanoma is rare but has a worse prognosis when diagnosed late due to the tendency to misattribute it to trauma.

Green Nails: The Pseudomonas Pattern

Green nail syndrome (chloronychia) results from Pseudomonas aeruginosa colonizing the space beneath a nail that has separated from its bed (onycholysis). Pseudomonas produces pyocyanin and pyoverdin pigments that stain the nail plate green-black. Treatment requires trimming the onycholytic portion to remove the bacteria’s protected environment, keeping the nail dry, and applying topical gentamicin or ciprofloxacin solution to the nail bed. Systemic antibiotics are rarely needed for isolated green nail syndrome in immunocompetent patients.

Nail Discoloration Evaluation at Balance Foot & Ankle

We evaluate toenail discoloration at our Howell (4330 E Grand River Ave) and Bloomfield Hills (43494 Woodward Ave #208) locations with clinical examination, nail culture or PAS histology for suspected fungal infection, and dermoscopic evaluation for pigmented lesions. When nail findings suggest a systemic condition, we coordinate referral to the appropriate specialist. Call (810) 206-1402.