CTB files are a deprecated file-type that was replaced by the STB file-type, which was object and not color-based. However, many companies continue to use CTB files and AutoCAD continues to support them. STB and CTB files cannot be used in the same project.

CTB files contain mappings of colors to the display objects which allow the objects to be rendered using the correct colors. STB files abstract this to object-based properties instead of color-based properties.