For orthorhombic single domains of YBa₂Cu₃O_7-x the a-b plane reflectivity and absorption are found to be anisotropic. For light polarized E||a the reflectivity is wavelength independent, but for E||b the vicinity of the Drude edge is announced by a smooth increase of reflectivity from the blue to the red, consistent with the free carrier contribution and dominating conduction along the 0(1)-Cu(1) chains. The strong increase of absorption (dichroic) in the range ~1.46 eV (850 nm) to ~3.38 eV (336 nm) and a shoulder at ~1.65 eV (~750 nm) are consistent with 0/sup 2-/ to Cu/sup 3+/ charge transfer and a Cu/sup ++/ d-d transition, respectively. The unexpected orientation and magnitude of bireflectance of layered ensembles of domains are suggestive of a higher resistance of the ensembles perpendicular to the walls.