I'm not sure if there is something I'm missing or only that I'm not high enough, but every node I've come upon in the first area of Coursant has been a rubat crystal, and that's all I get from gathering missions as well. Is a there a reason no green/blue ones are showing up? Am I just not in a high enough area?

Colour crystals in the world seem to be rare and well below the area level, my experience so far up to level 27.

all you need in early crafting is basically rubat, once you move away from cour you will be getting others. the tablets on the ground are the worst...

Hmm, yeah I guess when I played in beta, the coloured ones were everywhere and rubat was the rare one...:/

What's funny is I'm desperate for rubat crystalls to advance my artifice, but the GTN on Sanctum usually doesn't have any. Besides archeology, is there any other gathering crew skills that produces them? I haven't gotten any from treasure hunting.

I've gotten them from underground trading as well as some of the color crystals.

I found both crystals and artifacts at various locations once I had crew skills.

Power Crystal missions only give Power Crystals, which at the first tier is rubat. Color Crystal missions can give color crystals.

 

Now, sometimes you have more missions than your mission window will show, and the game randomly selects which missions it will make available. If you send crew out on the missions you have available, you may create space to let other missions in. So if all your seeing is power crystal missions, try a few of those, and you may let in the color crystal missions. Or else, you'll level up Archaeology, and that will give you access to more missions, some of which may be color crystals.