Prepare the pan by lining a 9-inch square pan with aluminum foil and spraying it lightly with cooking spray.

In a medium saucepan, combine sugar, unsalted butter, and half and half. Heat over medium heat, stirring until it reaches a rolling boil. Continue to boil for exactly 4 minutes while stirring.

Remove from heat and stir in white chocolate chips, marshmallow creme, and lemon zest until smooth and glossy.

Pour half of the mixture into the pan. In separate bowls, mix food coloring with 1/4 of the leftover fudge each.

Spoon the colored mixtures over the plain fudge layer, then pour remaining uncolored fudge on top. Drizzle the remaining colored mixtures on top.

Gently swirl the colors using a knife or skewer, being careful not to overmix.

Sprinkle jimmies or sprinkles on top while the fudge is still warm. Allow to cool completely at room temperature.

Once cooled, lift it from the pan using the overhanging foil and slice into squares.