of the device is measured in the range between 300 to 800 nm. The transmission spectrum under zero bias condition has been recorded as reference data, to see any variation in it after bias application. Under no bias condition, only ITO and EV$^{2+}$ (in PEO matrix) species are present and a peak appears around 560 nm. The peak around 560 nm gets suppressed as the biasing potential is increased and finally it changed into a valley shaped curve for a voltage of -3.5 V. It can be noticed from Fig.2 that there is not much change in %T at the wavelengths of blue (425 nm) and red (725 nm) colours as compared to the wavelengths in between these two. The device exhibited a minimum transmittance in the visible region at around 590 (orange-yellow) nm with a transmittance of 22 % at -3.5V. As a result, the counter colour of orange-yellow, i.e, blue, is observable to the visible eyes. This also means that blue color of the device in ON state is not due to the enhancement of blue wavelength but due to suppression of other colors in the visible range.

It is clearly observed from the transmittance spectrum corresponding to 