The reply to your question may be old but hopefully it helps you and other's as well.
I myself had this same issue and found a fix for it. Go to Open IV, search up the vehicles.meta file located in: GTA V\mods\update\update.rpf\common\data\levels\gta5
Then, using the built in text editor, open the vehicles.meta file in edit mode and press ctrl + f to search for the vehicle model you're having the issue with. In this case, it should be fbi2, once you've found that. Look for the diffuseTin tag for that vehicle, should be in the same list down below. Once you've found both the vehicle model and the diffuseTin tag for it, change the hex code value of the diffuseTin tag with this one: 0x00FFFFFF
That should clear up your tints and make them transparent for that specific vehicle, therefore solving the dark/blacked out issue with the lightbar. Now, just save and reload your game. It should be good now, hope this helps x3.
Hello, I know this has been posted on for a while but. I've ran into an issue with the model where the emergency lights don't seem to render or be in the correct place. I can see their reflection on the street and walls but they barely exist/illuminate on the vehicle model itself. Also, I noticed that after opening the ELS XML file to chnage the color of the lights to fit the skin I got. There was a typo left on line 4 where on the description a quotation mark was missing. I myself fixed it but the emergency light's issue still remains.