If you setup your interior as a black & white interior and do the same on Amazon KDP it will be printed in black and white.
However it may not come out very well, so you should convert the images to greyscale or black and white.
This is easy to do in the Book Bolt Studio.
Once you are in the Studio and have a image on a page, click on the image.
Click on the "Effects" button, then click the "Greyscale" choice.
Press "Ok" and your image has been converted to Greyscale.