According to Rıza Nur, sultan Selim I (1512-20) had a white personal flag, while the Ottoman Army flag was red (kızıl bayrak). During Süleyman I's reign (1520-66) the janissaries had a white flag while the timariot cavalry had a red flag. It was used as the Ottoman civic and merchant flag from 1793 to 1923.
According to Jane Hathaway (1 February 2012) A Tale of Two Factions: Myth, Memory, and Identity in Ottoman Egypt and Yemen[1], SUNY Press, ISBN 978-0-7914-8610-8, pages 99–
DarkEvil (former upload), TRAJAN 117 (current upload)