When I was meditating (lol) on the Saga today I came upon something-

All the Master and Apprentice pairs in the Saga all have the same color of lightsaber but Qui-Gon and Obi-Wan. Interesting. Even Luke when he chooses his new lightsaber's color chooses by chance or by Will of the Force green like Yoda.
I would guess Qui-Gon and Obi-Wan may have different colors to illustarte their nearly opposite thinking about the Jedi and the way they act. Obi-Wan is reckless and sometimes impatient while Qui-Gon is collective and calm.
Very well done GL!