Nonreciprocal directional dichroism, termed the optical magnetoelectric (OME) effect, has been observed in patterned superlattice (SL) composed of perovskite oxides, LaMnO3, SrMnO3, and LaAlO3. Such a tricolor SL with ferromagnetic interfaces is expected to artificially break both space-inversion and time-reversal symmetries and hence to show the OME effect. The Bragg diffraction from the grating structure with a period of 4 microm fabricated on the SL was employed to sensitively detect the OME effect, yielding the relative change of the diffracted light intensity (~0.2%-0.5%) upon a reversal of either the in-plane magnetization or the propagation vector of the diffracted light.