I don't know if the color of the fire has to do with what spirits they drop - I believe all of them drop blue and, if you're chaining kills, gray spirits anyway. Bomb and life fragments come at scripted events.
As for the number of life fragments, keep in mind that the first three stages are not especially long. Both stages and boss fights get longer as the game continues, so you'll see a steady increase in the later game anyway. Mefidex also claimed that he found something related to +3 fragments somewhere in the coding (obviously not used in the demo, though there was a fairy that dropped 2 in Stage 2). So we can assume that the full game will compensate for higher life requirements. I actually don't mind the apparently fewer resources this game gives so far, but that's only because I want the challenge. Something a bit closer to other shooting games, and perhaps something to force a bit more strategy in when to bomb/hyper bosses for scoring.