Because the paint says polar white its important to note that car paint is not pure white!. Its in the name, polar, like arctic or any other number of suffixes to the word white, actually mean its a SHADE of white not pure white.
You can of course just use the primer, which is white and then seal it with your clearcoat, or move away from car paint and use a can of appliance white which is oddly enough white!
The appliance white can be sprayed over your car primer, but car paints cannot be sprayed over the appliance white. This is because the car paints are either cellulose based or acrylic based to mix with each other, they react if sprayed over enamel which is what appliance white is.