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 μW 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‐developedn‐type conducting ZnSe substrates, green LEDs having external quantum efficiencies of 2.7% have also been demonstrated.