I Am An 18 Year Old Female Of South Asian

I am an 18 year old female of south Asian ethnicity. I have very dark discoloration on some parts of my body. I have noticed that is it mostly on areas where the skin is folded. It is mostly an issue on my neck, elbows, vaginal area and armpits. The skin in these areas look dark, ashy grey or purple giving it a lifeless look. These areas are very dry and I want to stress that it is very dark compared to the normal color of my skin. I am rather light for a south Asian. What causes this and what can I do to reduce it?