The flag of Sudan used since 20 May 1970 consists of a horizontal red-white-black tricolour with a green triangle at the hoist. The flag is based on the Arab Liberation Flag of the Egyptian Revolution of 1952. Upon gaining independence in 1956, Sudan, adopted a horizontal tricolour of blue, yellow and green. This flag was abandoned after the the 1969 military coup of Gaafar Nimeiry.
Learn more on Wikipedia