Under white ambient illumination and without bias, a reflective organic light-emitting device (ROLED) comprising a microcavity cathode exhibited various colors for static information display applications by means of internal interference and absorption effects. The configuration of this microcavity cathode was a metal/organometallic/metal structure of Al (10nm)/Ag (15nm)/Ag nanoparticles doped inside tris(8-hydroxyquinolinato) aluminum (Alq3) (xnm)/Al (100nm) with excellent conductivity. The thickness of the Ag:Alq3 played a crucial role in determining the reflection color; for example, varying it from 20, 40, 60, 80 and 100nm yielded the colors light yellow, light orange, reddish purple, greenish blue, and light green, respectively. In the dark, this ROLED can be used to display information with an ultra-high contrast ratio by applying on a small bias, like conventional OLED displays. Hence, this ROLED is a highly promising candidate for applications in energy-saving electronic fixed-pattern signs, logos, indicators, and manual information displays.