Its not paint Shawn. Those that appear to have a metallic skin or sheen to the have been coated with powdered mica product that usually goes into the raw plastic prior to cooking it. The powder in some instances is called a hi lite if it doesn't add any color or doesn't affect the clarity of the plastic its put in. If the powder adds color to the plastic, changes the color in any way, or makes the plastic opaque then its referred to as a pearl. Both types of powders have been used in these examples either in the plastic or has been brushed on dry after the bait has been made.
The ribbed work with the chartreuse tail has a violet hi lite in the purple colored plastic used for the top of the bait and is "just " visible on the tops of the ridges. The other baits have been dry brushed. The blue-green/gold minnow has been finished with pearl powders. The three purple baits have been dusted on the backs with a purple product used in automotive paints. The same purple is used on the second bait down of the four along with the hot pink automotive product used on the back of the bottom bait of the four baits. The other two baits in that picture and the one that's got the thin metallic sheen of varying colors are done using products that are used in the glass making industry.
The eyes and this powder coat need to be sealed and all of these baits have received a clear coat of plastic that has a dose of uv enhancement add to it so they stand out in all kinds and colors of water. Once the clear coat is applied the baits' colors and finish is pretty well protected.
Some person make simple baits using clear plastic, then airbrush acrylic colors on them. They too need to be clear coated as soon as the acrylic has dried. Myself I use plastic ranging from clear to maybe a smoke back or maybe purple...any color that will work within the direction I want to finish the bait in really. As seen many baits will get a color line injected thru them to help fire up the tails a bit. In clear plastic or the clear plastic with lots of silver/fire-opal glitter in it I like the line colors as they add color from inside the bait that works off the underside of the hi lite or pearl film added to the outside of the bait when kept in a relatively thin in coat.
Its fun stuff to work with. No two baits are the same...maybe close but never the same. And yes, they catch a lot of fish.