ColorCode
From Just Solve the File Format Problem
ColorCode is a two-dimensional "bar code" that uses colors to encode data. It has been referred to as a "3D bar code" because it has color depth as its third dimension. (There have even been references to "4D bar codes" consisting of something like a ColorCode being displayed on a monitor or phone display in a manner where the colors keep changing, adding time as a fourth dimension.)
ColorCode is a proprietary system (covered by US patents 6,981,644, 7,020,327, and 7,487,914) which was developed in Korea and is used mostly in Asia.
ColorCode bar codes might not actually look like bar codes; it is possible to "hide" a ColorCode in an image or colored text piece, as long as the proper pattern of colors is present.
