Back during the Civil War, there was a Confederate battalion based here in Louisiana. The troop was name the "Fighting Tigers of Louisiana"...This troop of tigers wore uniforms of pale purple and yellow into battle.
This is where LSU gets their moniker of The Fighting Tigers and maybe the fact that the confederate battalion wore the same colors as the team, purple and gold, is a coincidence but I'm not sure. While the Mardi Gras story sounds more P.C. and happy the civil war certaintly makes sense...