Laser diodes with the multilayer heterostructure have been observed in cathodoluminescence (CL) images using an analytical color fluorescence electron microscope. An AlGaInP/GaInP chip, which is commercially available as 670 nm red laser diode, emits red CL from a part of the p-AlGaInP layer just above the p-GaInP layer and between the n-GaAs blocking layers. A chip that has no blocking layers emits only very weak red CL, which indicates the strong relation of CL with laser emission. In images of a CdZnSe/ZnSe diode that emits 530 nm blue laser light at room temperature, a blue CL emission appears which is much stronger in the n-type region, in particular in the n-ZnSSe cladding layer, than in the p-type region