Its a story mission just keep playing the main story

You can change it at lightsaber upgrade tables (there's one at the back of the Mantis and a few scattered around the planets). I started out with green & blue (I think they're the defaults). You unlock all the other colours when you visit Illum and can change and equip them at any lightsaber table. To my knowledge, the colours and how you unlock them is a set process - your actions won't make a difference.

If you haven't gotten the extra colors yet then it's a spoiler.

There is a point in the main story that you getting choose your lightsaber crystal (you can change it later at any workbench). But before that you have blue, green, and orange(only if you got the dlc thing). You can change this at a workbench anytime. Also, once you beat the game, and start a new game plus, you can change your appearance from regular cal to inquisitor cal and you get a red lightsaber.

There is a point in the main story that you getting choose your lightsaber crystal (you can change it later at any workbench). But before that you have blue, green, and orange(only if you got the dlc thing). You can change this at a workbench anytime. Also, once you beat the game, and start a new game plus, you can change your appearance from regular cal to inquisitor cal and you get a red lightsaber.

Why did that save twice

I found that when using a lightsaber as a light, orange gives the clearest view