type of primer

What color primer should i use. Im painting my car sonic blue clearcoat. I bought a lite gray. Ive heard around here people use white primer and black for darker colors. Ive already sprayed my car with the lite gray primer. i didnt spray any primer on my plastic pieces and the color came out a dark color.
Heres a picture i want it to come out to look like. And heres another picture of what my car did turn out to look like but im redoing it because of the clearcoat looked like crap. And here is a picture of my primer.http://i42.photobucket.com/albums/e332/copus123/Diecast%20Mustang%20Saleen/IMG_0262.jpghttp://i42.photobucket.com/albums/e332/copus123/Diecast%20Mustang%20Saleen/IMG_0269.jpghttp://i42.photobucket.com/albums/e332/copus123/saleen/608796_22_full.jpg

I want the color to look like the one on the car.