[DSM-Mark]

It is the paint that produces that effect. However, it is usually both a process and a paint. Most flip paint jobs require a base coat, then a color/flip coat, then a clearcoat. If you add a primer coat, that is a minimum of 4 individual layers that must be applied.

A lot of people use Duplicolor's color flip paint, which requires the 3 coats I mentioned above. However, most often the flakes look out of proportion to the car, as the flakes are designed to go on something 24 times the size of your model car. There are other options as well, though. Nail polish is one, but be careful with it, as it often goes down 'hot', meaning it can melt/distort the plastic body. A good primer coat is a must if using nail polish, and even then you should test on a scrap piece first. Another option is Alclad's prismatic line-up, which again requires a base coat and clearcoat for the right effect. Alclad is also fairly expensive. Check your local hobby stores for this stuff. It comes in a small glass bottle (1 think it's 1 oz) and goes for about $12CDN ($9US) a bottle. At least up here it does.

EDIT: You also need an airbrush to apply both nail polish and Alclad.