Most vehicles will get a random tint chosen from a customizable color pool.
You can modify the pool of possible tints by editing the file DefaultTints.ini

I've made a configuration DefaultMaps.ini for LW b15f3 only, other version can support it but they need setting up the DefaultMaps.ini

Install instructions:

Copy patch_recolor.upk in ...\steamapps\common\XCom-Enemy-Unknown\XEW\XComGame\CookedPCConsole

Copy the 2 INIs from the folder "LW b15f3"  to ...\steamapps\common\XCom-Enemy-Unknown\XEW\XComGame\Config

This will replace the LW DefaultMaps.ini