Here's the Wikipedia entry of the Broncos old jerseys:
When the Broncos debuted in 1960, their original uniforms were vilified by the public. It consisted of brown helmets, brown pants (some had a satin sheen, some didn't), white and mustard yellow jerseys, and vertically striped socks.[21] The club eventually got rid of these jerseys two years later, and celebrated the occasion by holding a public bonfire to burn the striped socks.
Also, the Dallas Cowboys played the Dallas Texans, now KC Chiefs, today. The old Cowboys jerseys were bad too. The old Texans look was actually much the same as the current Chiefs, except for the logo on the helmet.