Prepare the Pan: Line a 9-inch square pan with foil, spray with cooking spray.

Cook the Base: Combine sugar, butter, and half and half in a medium saucepan over medium heat. Stir constantly until it reaches a rolling boil for 4 minutes.

Mix in the Goodies: Remove from heat and add white chocolate chips, marshmallow creme, and lemon zest. Stir until smooth.

Color the Fudge: Divide fudge into three bowls. Add food coloring to two bowls and mix until vibrant.

Layer the Fudge: Pour half of the plain fudge into the pan. Dollop colored mixtures on top, pour remaining plain fudge over.

Swirl for Effect: Use a knife to gently swirl the mixtures without fully blending them.

Add the Finishing Touches: Sprinkle jimmies or sprinkles on top and let sit at room temperature until cool.

Cut and Serve: Once cooled, lift fudge out using the foil overhang and cut into squares.