How to print a presentation (ppt) file in the most economic way?

Question

I have a presentation with several images and a dark background. So it should be very expensive printing it.
Is there a way to printing in a "toner saving mode", ie, just black/gray color font over white background.
Mostly I ask for a software configuration way. But hardware solution is welcome too.
I am using "libreoffice" in linux and my printer is a Samsung ML-3471ND (laser B/W).

EDIT: Something like Edit->[print in a very economic mode] or Format->[automatically turn background to white and foreground to gray scale] etc... or maybe some printer setting.

EDIT 2: @diogo-rocha Why deleted your answer and my (an another user's) related comments? What is the constructive idea behind that behavior? Please think first in the community convenience.

Answer 1

I had to test this to believe it. I think I found the answer though. The presentation in the screen shot is normally white text on a dark blue background. When I put it to grayscale, it goes monochrome and inverts.