Pour lemon yogurt into a bowl and the key lime pie yogurt into another. Equally divide the white chocolate mixture between the two bowls. Stir to combine. Fold 1/4 cup whipped cream into each of the bowls of yogurt. Color lemon mousse with yellow food coloring and the lime mousse with green and yellow. Spoon lemon mousse, lime mousse, and the whipped cream into three disposable pastry bags or zip-top plastic bags.