Melt white chocolate according to package directions.
Add in drops of yellow, orange, red, and green oil based food coloring. With a toothpick, gently swirl the colors but don't mix in completely.
Pour a little melted chocolate into each open spot on the mold. Tap the mold a few times to get any air bubbles out. Using a clean food paintbrush or spoon, "paint" the chocolate up the sides of the mold. Allow to dry.
Once the chocolate is dry, press the Oreo truffle dough into the mold.
Pour remaning white chocolate on top of the truffles to seal the spots in the mold. Run a knife or bench scraper over the chocolate to smooth out the top. Allow to dry.