OK, that model is on the list. The Mac OS typically comes with printer drivers/software for numerous printers, including all the ones for Canon on that link that I provided above. Then again, Canon has specific driver software for your printer that is compatible with OS 10.12.x:
https://canonpixmadriver.com/2016/09/11/driver-canon-pixma-mg5600-series/
I have a Canon PIXMA MX890 printer with my late 2012 MacMini and OS 10.12.5, and I just use the drivers that come with the Mac OS. Are you using OS 10.12.5, the latest version of Sierra? This link explains how to just print in grayscale:
https://www.cnet.com/how-to/the-buried-mac-setting-that-can-save-your-inkjets-color-ink/
By the way, note what it says on the bottom of that link:
"
Editors' note, July 14, 2014: This article was updated to reflect the fact that the layout of the print screen varies from manufacturer to manufacturer and even model to model within the same manufacturer."