That's pretty straightforward.
Arrange your LEDs in strings of 8 LEDs connected in series with a current limit resistor, 4 strings per color.
Each string will require <=20 mA from a 16-20V source. Wire the 4 strings in parallel.
Obtain a DC upconverter from pololu.com such as this
Pololu Adjustable Boost Regulator 4-25V
to convert the car's 12-14V up to the 20V or as needed for your particular LEDs.
Then a single NPN or MOSFET transistor such as IRF3707Z can be driven by the arduino to turn each LED collection on & off.