Story line at lvl 50( warning spoilers)

[Alanto]

Ok when you kill ultima weapon there is cutscenes, and at the end there is roar and Crystals new color perple(was blu):
1) roar- was it bohamat?
2) crystal was infected by darknes and now is evil?

[Fear]

If you read it properly it was the primals, that's why you kill ifrit first

[LiadansWhisper]

1) The Roar is most likely Bahamut.
2) The vision of the Crystal appears to be foreshadowing/a prophetic vision.