The 0th resonant diffraction characteristic of the embedded grating with incident angle of 45° is analyzed by the rigorous coupled-wave theory. The resonant wavelengths of 0th reflection light are 432 nm and 420 nm for the TE and TM polarization respectively in the plane parallel to the grating vector. The resonant wavelengths of 0th reflection light are 623 nm and 620 nm for the TE and TM polarization respectively in the plane perpendicular to the grating vector. The resonant wavelength of 0th reflection light is far different between these two planes and shows different color. That phenomenon is denoted as dual-channel characteristic and is proved in experiment. The metachromatic device with dual-channel characteristic is made.