Disclosed are a sheet buffer module and a printing system incorporating the buffer module. The buffer module has parallel first and second sheet transport paths that extend in opposite directions across a frame. Sheet buffer paths connect the first sheet transport path to the second sheet transport path. In operation, a stream of sheets is fed by the first sheet transport path from a multi-color printing module to a monochrome printing module. During this process, selected sheets are diverted from the stream into the sheet buffer paths and held. After processing by the monochrome printing module, the stream is fed by the second sheet transport path back to the multi-color printing module for further processing and/or final output. During this process, the sheet buffer paths feed the buffered sheets into the second sheet transport path such that they are inserted at the proper locations back into the stream.