A group of rebels known as the Federalists declared a republic based on the Mexican Constitution of 1824. The new state was to include the Mexican States of Coahuila, Nuevo Leon and Tamulipas, with its capital at Laredo. The Republic of the Rio Grande was declared in January 1840.
A January 25, 2005 email explains the color of the lower stripe on the Republic of Rio Grande Flag.
"My name is Ricardo Villarreal. I'm the director of the Republic of the Rio Grande Museum in Laredo, Texas.
"Our most prominent historian, Dr. Jerry Thompson, a professor at Texas A&M International University says the color in question was green on the original flag. He says that the original flag, which was captured by the Centralistas, is probably in storage at Chapultepec Museum.
"Another early local historian somehow made the mistake of changing that color from green to black, which has been used since the 1930s."