If you want the car to spawn with liverys when using one of the livery sets you must add "+livery" flag at the end of the data line.

Simply replace the vehicles.ide line from the original readme with this one.

sentinel3,	sentinel3,	car,		SENTINEL,	SENTINEL,	VEH@STD,               NULL,			10,	5,		0.2207,	0.2207,		0,	5,	1.0	,1,	ext_sunroof+ext_strong+livery