Line 8x8 pan with parchment paper, leaving paper overhanging the edges of the pan. This will allow you to pull the paper and remove the fudge at the end. Spray parchment with cooking spray.
In large microwavable bowl, microwave white chips uncovered 30 seconds. Stir and microwave 30 more seconds.
12 ounces white chocolate chips
Spoon frosting over chips and microwave 30 seconds. Stir. Microwave again in 15 second intervals until the mixture is smooth.
1 container vanilla frosting
Evenly separate the chocolate mixture into 3 bowl.
Add green food coloring into one bowl and stir until desired color is achieved. Do the same with red. And leave the third bowl white.
green and red gel food colors
Drop heaping tablespoons of green, red and white fudge into the prepared ban creating a random pattern. Pull table knife through layers for marbled design.
Refrigerate uncovered until set, about 1 hour.
Remove fudge from pan and cut into squares (8 rows by 8 rows). Store covered in refrigerator.