Darnath

The enhanced version of GTA V is not yet supported for LSPDFR but I think they're working on it, you need the legacy version for it to work.
 
 

Easier to do it by editing the awc file.

Found the solution !
 
https://www.gta5-mods.com/tools/ymap-load-list-extent-limit-fix-fwboxstreamervariable-patch
 
Adding this fix the issue.
 
Thanks for your help !

You can edit those in the "vehicles.meta"
 
Search the line "<diffuseTint value=" and set up like this for no tint :  <diffuseTint value="0x00FFFFFF" />
 
If it still doesn't work, it's maybe a texture problem, go to your sheriff2.ytd
In it, search for your "window" texture, the name can varry with the model, you can edit it to fit your licking.

Try this video, I had issues too with installing EUP, but a lot of tutorials are bad and don't mention the way to fully install it, to make it work on NPC. You're likely missing the backup eup uniforms mod.
 
Since your game crash, try to unistall all EUP related content, watch if the game still crash and then follow this video :
 
 
 
 

It's ; 
policegauntlet (the "camaro" interceptor)
 
police5 (the special CW)
If you ever doubt, go to ;
 
\Grand Theft Auto V\lspdfr\data
 
and search for "duty_selection" and "agency", in those files you can see all vehicles list and edit the fleet of each departement at your liking.
 
(If you use EUP, go to \Grand Theft Auto V\lspdfr\data\custom, and search thoses files with "_EUP" added to them)