high intensity discharge headlamps.
short tut;
use a soft brush at 0% hardness at linear light.
copy the headlight into a new layer [layer via copy]
for a nice white/blue, use the color 'C5DCFF'.
adjust brush size to the projector's size, click once or twice depending on how much you want it to 'pop'. [i set my brush to 50% at first in a more daytime setting]
if you wanna be awesome [like me
] do like what i did in my sig
good luck!