Communication: Color or spectral tuning of light emitted by LEDs based on conjugated polymers is important if such LEDs are to find applications in multicolor display devices. A copolymer system is described in which the wavelength of the electroluminescence can be controlled by the external voltage applied. Following an account of the monomer synthesis and copolymerization route, features of the photoluminescence, absorption, and electroluminescence spectra are reported and preliminary ideas presented about how to explain the results.