Wyner-Ziv coding of multiview images avoids communications between source cameras. To achieve good compression performance, the decoder must relate the source and side information images. Since correlation between the two images is exploited at the bit level, it is desirable to map small Euclidean distances between coefficients into small Hamming distances between bitwise codewords. This important mapping property is not achieved with the binary code but can be achieved with the Gray code. Comparing the two mappings, it is observed that the Gray code offers a substantial benefit for unsupervised learning of unknown disparity but provides limited advantage if disparity is known. Experimental results with multiview images demonstrate the Gray code achieves PSNR gains of 2 dB over the binary code for unsupervised learning of disparity.