Specify monochrome settings on the application side so that the print request is sent as a monochrome data to the on-demand terminal.
However, in applications such as Word, monochrome data may not be produced as intended, so please refer to the FAQ below for concrete methods:
Even if I send a print request in monochrome setting from Word, for some reason it becomes in color setting on the on-demand terminal.
https://www.u.tsukuba.ac.jp/ufaqs/en-printing-mono/