Line an 11x7 baking sheet with parchment paper and set aside.
Place the broken up white chocolate in a microwave safe bowl and melt on a low setting, stirring every 30 seconds, until smooth. You can alternatively use a double boiler to melt it instead.
Separate 2-3 tablespoons each of the melted white chocolate into two separate small bowls and add 1 drop of different food coloring in each. Stir it together with separate spoons.
Pour the uncolored melted white chocolate on the prepared baking sheet and spread it out with an icing spatula or back of a spoon.
Drop small spoonfuls of the colored melted white chocolate in alternating colors then use a skewer to swirl the colors together.
Before it hardens, add the Lucky Charms marshmallows on top, followed by sprinkles.
Let the bark set at room temperature for 30-45 minutes until the chocolate has fully hardened. You can also place it in the refrigerator for 15-30 minutes to help it set quicker.
Once it has hardened, use a knife to cut it into neat bars or you can break it apart with your hands.