The tailoring of the chromaticity of white organic light-emitting diodes (WOLEDs) has presented a significant challenge in their application in smart lighting sources to improve the quality of life and human performance. Here, a new microcavity WOLED (M-WOLED) structure to modulate the chromaticity of the emitted light is demonstrated by only adjusting the thickness of the white light-emitting layer. By introducing a polymer-metal hybrid electrode that functions both as a partially reflective mirror and a transparent electrode, a very simple microcavity architecture that does not require additional outer mirrors, such as distributed Bragg reflectors is developed. The resulting M-WOLEDs exhibit reddish-, greenish-, and bluish-white colors with different thicknesses of the single white light-emitting layer.