Star Wars lightsaber colors often reflect a Jedi's function, attitude, or narrative decisions. Obi-Wan Kenobi's lightsaber was blue for storytelling and production reasons, not in-universe reasons. Some major points:
1. Traditional and Symbolism: The original Star Wars trilogy did not assign lightsaber colors connotations. Blue for Obi-Wan's lightsaber in "Star Wars: Episode IV - A New Hope" was more traditional and practical for visual narrative.
2. Contrast and Visibility: Star Wars films include fast-paced lightsaber combat, thus distinguishing characters is key. Obi-Wan's lightsaber was blue to provide contrast and help audiences follow the action, especially with limited special effects capabilities.
3. Production Choices: Early Star Wars films had less distinct lightsaber colors. The 1970s and 1980s' visual effects technologies affected lightsaber colors, because blue was practical and fit the film's aesthetics.
Obi-Wan's blue lightsaber in the original trilogy was more for visual narrative and practicality than a specific in-universe purpose related to his character or duty in the Jedi Order. Later Star Wars stories and media gave lightsaber colors more symbolic value.