The color of a car's paint can vary when viewed at different angles as the clearcoat can refract light like a prism -- thereby changing the wavelengths that are observed. Every paint does it -- some more than others.
Dupont had that Mystic Green metallic on the Cobra few years ago. The properties of that paint allowed a viewing spectrum from green to purple to brown to orange. The problem with that paint is that if you had damage to one panel -- the whole car had to be redone.
Also, the paint application process itself can vary -- thereby slightly changing the color -- given the atmospheric conditions that it was applied in, etc. Yellow Jacket, a pretty simple color, has four distinctly different variations in 2004 alone. Some other cars, like the Chrysler 300, have single paint colors that have a dozen different variations.