Registration black

In printing, registration black is a black color that includes 100% of each of the process colors used. Typically these are cyan, magenta, yellow and black (CMYK), but if different colors are used, registration black marks are made with all of the colorants (inks).

Registration black is used for printing crop marks and registration marks. When proofs for each color are generated on separate pieces of film, use of registration black makes crop marks visible on all channels, providing a useful reference for alignment. A thin line printed in registration black can also be used to check whether the printing plates are aligned.