This paper presents a low-power encoding technique, called chromatic encoding, for the Digital Visual Interface standard (DVI), a digital serial video interface. Chromatic encoding reduces power consumption by minimizing the transition counts on the DVI. This technique relies on the notion of tonal locality, i.e., the observation that the signal differences between adjacent pixels in images follow a Gaussian distribution. Based on this observation, an optimal code assignment is performed to minimize the transition counts. Furthermore, the three color channels of the DVI may be reciprocally encoded to achieve even more power saving. The idea is that given the signal values from the three color channels, one or two of these channels are encoded by reciprocal differences with a number of redundant bits used to indicate the selection. The proposed technique requires only three redundant bits for each 24-bit pixel. Experimental results show up to a 75% transition reduction.