Eating lots of junk food or sugary snacks can cause a pasty coloured skin, which can be resolved by eating lots of fruit and vegetables and foods that are high in Vitamin C.
My people call it poisonous food"virudha aharam" , like recipes don't match each other , example fish and curd will cause some kind of reaction which is harmful to the human body and it can lead to skin disorder , which includes discoloration of the skin