now that that's off my chest, Nice piece! Since I can't colour to save my life, I'm jealous of missing that tutorial. I need to sit down with some of my Photoshop gurus at some point... friend of mine did the colouring for the reissued Conan comics, all in photoshop of course.
I make a new layer for the beam, create the shape and fill it with the color of the blade, then do an inner glow from the center in white and an outer glow in the color of the blade.