Grease three 9-in. round baking pans; set aside. In a large bowl, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Combine 2-1/2 cups of cake flour, baking powder and salt; add to the creamed mixture alternately with milk.
Divide batter into thirds. To one portion, fold in melted chocolate and vanilla. To second portion, fold in 1/4 cup flour, almond extract and 3-4 drops red food coloring. To third portion, fold in lemon extract, 3-4 drops yellow food coloring and remaining flour.
Spoon a ring of chocolate batter around edge of one prepared pan; spoon a ring of pink batter inside chocolate ring and fill center with yellow batter. Spoon a ring of yellow batter around edge of second pan; add a chocolate middle ring and a pink center. Spoon a ring of pink batter around edge of third pan; add a yellow middle ring and chocolate center.
Bake at 350° for 20-25 minutes or until a toothpick inserted in the center comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.
For frosting, in a large bowl, cream butter and 2 cups confectioners' sugar until light and fluffy. Beat in melted chocolate until smooth. Add milk and vanilla. Beat in enough of the remaining confectioners' sugar until frosting achieves spreading consistency. Spread between layers and over top and sides of cake.