In the Star Wars: Republic series, multiple Jedi have red lightsabers. Given the association between red lightsabers and the Sith, why is this? I'm looking for both the in-universe and out-of-universe reasons.
I haven't heard of the Star Wars: Republic series, but I do know that the color of the lightsaber doesn't necessarily denote whether you are a Dark side user or a Light side user. It depends on you. A Jedi could have a red lightsaber. That doesn't mean he is a Dark side user. He could have gotten it from a Sith he defeated in battle if the Sith was using a red saber. Just like you can take a blue lightsaber even if you are evil, like with General Grievous. Also, artificial kyber crystals usually are red and produced a red colored lightsaber blade, but a Jedi could use an artificial kyber crystal if they wanted, but still be a Light side user.