So the hair....
Ok, so the hair should be alternating colors between shades of vivid red and blond, with darker shades of blond/orange to help them blend together/seem more natural. Below is sort of an idea of how i want them to alternate, though it is with a blond and brown haired person instead XD
As for an idea for the color....fire. Just, fire XD
Whatever makes it come off as more firelike. It is his natural hair color, so just like natural hair, if a random shade of black or other colors are needed to pull off the shades, that's perfectly fine. Aiden is the flesh bound form of a fire deity (though he doesn't know it), so that's one of the major reasons why his hair is like this.
Note: His hair should come off more dark than light though, so try to focus more on the reds
3nodding
I think you can get a bit of an idea of the style from the black and white picture. I would say pull from there first, then use what I say here to fill in the blanks.
Basically he tries to keep up his appearance, though he lets his hair grow out a bit. While on special occasions he may style it back, most the time he lets it fall freely, giving him some bangs and strands framing his face. It is a little uneven (he doesn't get his hair professionally done), and it may seem a little longer/fuller on one side of the face than the other, sort of like if a person parts their hair to one side. I am hoping that when it is in color, it will have a bit of a flame feel to it.