In your lights.ini you will see the hex color code for every light source, like break light, head lights or tail lights. White usually is something like 255,255,255. So 255 is the maximum one of the threee entries can have as a color. But according to the Assetto Corsa pipeline, increasing the first digit by 100 or more will make it brighter, so 655 for example.
Take for example the Porsche 911 RSR, the lights.ini says
[BRAKE_0]
NAME=Brake_light_1
COLOR=550,0,0
OFF_COLOR=0,0,0
So they increased the number from 250,0,0 here to 550,0,0 to make it brighter.
I am currently fighting some shader issues with my rear light glass, so I won't see much light coming through anyways, but when I increased that value the ground behind the car became much brighter. Perhaps that also works for the distance, who knows?