Fasting on Sunday, or Ravivar Vrat, in Hindu religion is dedicated to Lord Surya, or the Sun god. Hindus have been worshipping Surya Narain from time immemorial and is also occasionally referred as Pratiyaksha Brahman. There is a popular belief that observing fast on Sunday will help in skin and eye ailments.
The fasting is from Sunday morning to next day morning. A single meal is taken on the day, generally after sunset. Some people only eat fruits on the day. Those who eat cooked food avoid salt and fried food items.
Red is the color of the day. Devotees offer red colored flowers to Lord Surya. Red sandalwood paste tika or tilak is worn on the forehead.