//top of script
new GroveCar[10]; // or however many you want

//under OnGamemodeInit
GroveCar[0] = AddStaticVehicle(etc.) // Arrays start at 0, and it counts as 1
GroveCar[1] = 
.
.
.
GroveCar[9] = 

// You have 2 options. You can set all the car colors to green in spawn info^ OR make a foreach loop:
for (new i = 0; i<sizeof(GroveCar);i++)
{
ChangeVehicleColor(GroveCar[i], 128, 128); // Sets all GroveCars to Green on spawn
}

// You would have to do this process for each of the gangs, but I hope this is a helpful start. :)

new GroveCar[2];

GroveCar[0] = AddStaticVehicleEx(536,2508.2949000,-1668.1362000,13.0688000,0.0000000,-1,-1,15); //Blade
GroveCar[1] = AddStaticVehicleEx(535,2502.2048000,-1657.6660000,13.1479000,53.9400000,-1,-1,15); //Slamvan

for (new i = 0; i<sizeof(GroveCar);i++)
{
    ChangeVehicleColor(GroveCar[i], 128, 128);
}