I thought the blaze of blue light in Goblin Town was awesome! I really liked how that, along with the accompanying sound/shock wave, portrayed Gandalf's immense and otherworldly power.

I was referring to the use of multi-colors in the pine cone scene:

"He gathered the huge pine cones from the branches of his tree. Then he set one alight with bright blue fire, and threw it whizzing down ... Then another came and another, one in blue flames, one in red, another in green. They burst on the ground in the middle of the circle and went off in coloured sparks and smoke."

It mentions multiple flame colors, sparks, and smoke - so that's where, to me, my mental imagery wanders off into fireworks territory. And when I picture them up there in the trees, desperate, surrounded by raging wargs and orcs, then picture them surrounded by colorful flames, colored sparks and smoke, that seems incongruous to me. That's just how I see it. Now if you are saying the whole thing could have been done with the same type of blue fire - and blue fire only - that was used in the Goblin Town scene, I think I see where you're going with that, and I agree, especially given the darkness and the overall feeling of the scene, that a blue fire would have been very impressive too.