This darkening occurs when an excess of melanin, the brown pigment that produces normal skin color, forms deposits in the skin
Treatment involves hydroquinone, azelaic acid, corticosteroids, tretinoin cream and laser
treatment. Pls discuss these options with your dermatologist before using them.Cold skin and blue peripheries can be due to Raynaud’s phenomenon or peripheral vascular disease.Pls get it evaluated from a physician.
Hope it helps.