I thought that was his hand charging up the spell, I was watching that at a lower quality though, nice find.
It's amazing how much of this still falls in line with what Nomura said many, MANY years back. I remember him saying that Noctis' hair and eyes would change color depending on something (Magic? Mood?). That was back around 2007 or 2008 I believe (Back when the characters' names hadnt' been revealed yet).
So, from Nomura's information back in the old age, we got:
1) Game will feature big, open maps (Confirmed, and we are actually seeing them now).
2) Chocobos will be there, and we will ride them (Confirmed by Tabata during the conference).
3) There will be a car we can drive through the overworld (Confirmed, we are seeing it now).
4) There will be controllable airships. "We have an airship flying over the overworld now", Nomura said. (Not yet confirmed, we haven't seen anything).
5) Noctis will carry a cell phone around to take pictures/screenshots of the scenery. (We haven't seen it yet. Maybe it was scrapped due to the new consoles having a built-in screenshot feature? A photo mode would be very nice).
6) Moogles will appear, and their designs will be similar to the ones in Type-0, very Kingdom Hearts-like. (We haven't seen them yet).
7) Something important about Noctis wearing a ring? (We haven't heard about that since then).
8) Nomura says more vehicles will be available. A person interviewing him asks for a motorcycle. Nomura laughs and says "maybe". (We haven't seen a bike yet).
9) The overall plot will be very simple, and the game instead will focus on friendship and bonds instead of the "grand scheme of things". (Seems like it so far).
Anything else I'm missing?
EDIT: probably his hands are glowing not his hair?
No, it's definitely the hair. Watch the video in slow motion, there are at least 4 frames of his hair glowing in different intensities. After the Behemot burst into flames, his hair glows bright orange for a second.