I Have read your question ,
Fair /Dark Complexion is generally due to the exposure to direct sun , or sometimes genetic reasons too. Skin darkening is due to the increased melanin
pigments on the skin.
You can use skin lotions like sunscreens with spf16 or above , and alternatively you can use natural remedies like Yogurt (=curd)+lemon Pack, aloe vera
face packs , sandalwood packs etc. these are quite effectively also.I would also suggest you to cover you exposed parts with the help of gloves or scarf etc.
I hope This helps you ,