A New Angle on Cheap LCDs: Making Positive Use of Optical Distortion

When viewing LCD monitors from an oblique angle, it is not uncommon to witness a dramatic color shift. Occasionally, this can appear as a total color inversion. This is primarily caused by a polarization asymmetry, where light rays passing through the pixel matrix at oblique angles are influenced by the relative orientation of the liquid crystal (see paper for more details).

by (http://chrisharrison.net/index.php/Research/ObliqueLCD)