My hair is growing Brown. The earliest.

I've got black hair, and by about last 2 years they started growing brown like dark brown shades. When sun light falls over my head after a shampoo head bath I brown colour is sort of awkward all the time. Like lite brown colour in the sun. When oil is applied it appears to be dence and hence dark brown and definitely not black. And I've got white hair growth too in the middle now they have raised in their numbers. Please suggest me a way to grow natural black hair. In my face my facial hair around my chin in growing light brown and it's very visible. I've attached a pic of my facial hair and I have them on both sides and rest of the hair are clean black. I don't have severe hair falls. Everything is very fine but the brown time of hair and my beard makes me worst. Please let me know at the earliest. Thank you docs in Advance.