The blue and the gray......blue for the North.....gray for the South..

Civil War Uniforms - HistoryNet

https://www.historynet.com/civil-war-uniforms

Uniforms at the beginning of the Civil War, however, showed greater variety than would ... Some Union units wore gray, while some Confederates were attired in blue. ... Primarily, however, regular U.S. Army troops wore their traditional dark blue trousers, ... which gave rise to the nickname "Butternuts" for Southern soldiers.