High-brightness blue and green light-emitting diodes (LEDs) operating at peak wavelengths in the range 489-514 nm have been successfully synthesized, processed, and tested. The high-brightness LEDs are II-VI heterostructures grown by molecular beam epitaxy at North Carolina State University using (100) ZnSe substrates produced at Eagle-Picher Laboratory by the seeded physical vapor transport process. The blue LEDs (489 nm) produce 327 mu W at 10 mA drive current with an external quantum efficiency of 1.3%. In terms of photometric units, the luminous performance of the ZnCdSe blue LEDs is 1.7 lm/W at 10 mA. The brightest ZnTeSe green LEDs tested to date produce 1.3 mW at 10 mA peaked at 512 nm with an external quantum efficiency of 5.3%. The luminous performance of the green LEDs is 18 lm/W at 10 mA. Using recently-developed n-type conducting ZnSe substrates, green LEDs having external quantum efficiencies of 2.7% have also been demonstrated.