Place the melted white chocolate in the bowl of a food processor.
In a small saucepan combine the cream and butter; place the pan over medium heat. Bring the mixture to a simmer, stirring occasionally, but don't allow it to boil.
With the food processor running, carefully pour the hot cream mixture through the feed tube into the white chocolate. Process the mixture until smooth, stopping to scrape the sides of the bowl if necessary. If the oil starts to separate from the white chocolate, continue to process until it becomes smooth again and has the thick texture of cake batter. Add the vanilla extract and process briefly to mix it in.
Scrape the white chocolate mixture into a bowl and chill in the refrigerator for 2 to 3 hours, or until very firm.
Dust your hands with powdered sugar. Form the white chocolate into balls, then roll one end of each ball between your palms and pinch it gently to make an egg shape. Place the eggs on a baking sheet covered with parchment paper or waxed paper. Refrigerate the eggs while you prepare the candy coating.
Melt the white candy coating in the microwave in 30-second increments, stirring after every 30 seconds to prevent overheating. Divide the white coating between 3 bowls--you will work with 1 bowl at a time, so keep 2 in reserve and just work with 1 initially.
Place each color of candy coating disks in separate small bowls. Melt each color of candy coating.
Use a spoon to drizzle several different colors of candy coating on top of the first bowl of melted white coating. The colors will mix together as you dip the truffles, so try to choose colors that blend well and won't immediately produce a muddy color. Don't worry about swirling them together -- the dipping process will handle that!
Submerge a truffle completely in the coating. Use a fork or dipping tools to fish it out of the coating. As you bring it out of the bowl, swirl it around a little to make sure that the top is coated with a variety of colors. Place the truffle back on the baking sheet, and repeat with the next truffle.
After dipping several truffles, the candy coating colors in the bowl will become indistinct, so at this point, drizzle more colored candy coating on top of the white coating to get vibrant swirls. Repeat until the coating in the bowl is too low for dipping or until the white coating is no longer white. Scrape the coating out of the bowl (it can be saved and used for another purpose) and use your reserved bowls of white coating just like you did the first. Repeat this process, using different colors, until all of your truffles are dipped.
Refrigerate the tray to set the coating, about 15 minutes. For the best taste and texture, serve these truffles at room temperature.