Necesita una consulta como esta:
SELECT * FROM car
INNER JOIN car_color ON car.id = car_color.car_id
LIMIT 1 -- this will limit the results to only one row
editar:para obtener solo un color para un automóvil, puede usar el grupo:
SELECT * FROM car
INNER JOIN car_color ON car.id = car_color.car_id
GROUP BY car.id -- this will group all the rows with the same car to only one row per car
