March 16, 2019
From the Welcome to Barcelona site:
If you visit Barcelona, you might be wondering what all the different flags you’ll see hanging from balconies around the city symbolize. The most common flag of them all is the Senyera, the flag of the autonomous region of Catalonia, with alternating red and yellow stripes(Here's an article about Barcelona's actual upcoming uniforms.)
There are several different theories of where the Catalan flag originally came from. The first appearance of the flag is said to have been on the tomb of Ramon Berenguer II, the Count of Barcelona who died in 1082. One legend has it that the Count had fallen injured in battle and created the Senyera while on his deathbed. According to the story, he stuck his fingers into his wound and drew them down his yellow shield, creating Els Quatre Dits de Sang, or “The Four Fingers of Blood,” that appear as four red stripes on the flag.