Preheat oven to 350°F. In a medium mixing bowl, cream butter. Add 2 cups flour and granulated sugar and mix until dough is smooth. Spread in Jelly Roll/Cookie Pan. Bake 10 minutes or until lightly browned.
For filling, combine firmly packed brown sugar and eggs; mix. Add 1/4 cup flour, vanilla and baking powder. Stir until blended. Stir in raisins. Pour over crust; bake 30 minutes or until filling is set. Cool.
Melt Candy Melts colors separately, following package directions. Drizzle melted candy over top of crust. Let set 5 minutes; cut into bars.