Quote Originally Posted by TheAbominatrix
All summons come from red, as did this one. Just because we dont see that particular materia being absorbed doesnt mean it wasnt. They use materia of all sorts of colors throughout the film and it only shows the green being absorbed. It's implied that they absorbed the rest. Just as we dont see the Turks being rescued on screen, but we know them to be rescued thanks to Vincent.

And yes, it was Bahamut SIN.
About the materia thing, no, it was a green materia. At the end with Yazoo and Loz, you see them using Materia of multiple colors and you see each color separately (purple, green, yellow, etc). The color glowing when Kadaj summons Bahamut Sin is green, implying the use of Green Materia.