There are few ways to choose whether to print in colour or B&W in MacOS and the method can change from application to application.
Following is a brief description of how to ensure you receive the desired colour output when printing.
This shows how to print in B&W from within PowerPoint. Follow the same steps to print in colour, replacing Greyscale with Colour where appropriate.
1. Choose "Print" from the "File" menu.
2. Next to "Output" choose "Greyscale" that'll tell Powerpoint to print it in B&W. Next from the Menu that currently says "Powerpoint" choose "Printer Options"
3. From the "Feature Sets" menu now shown choose "Color 1".
4. Next to "Color mode" choose Greyscale.
Now your print will print correctly in Greyscale.
For more help with this please email firstname.lastname@example.org