Powerpoint is one of the worst applications to print from, it is not at all intended for print and does not handle CMYK or the conversion to it at all well.
Realistically, any designer should know to output to pdf and print that, and don't take my word for it, take it from the guy who designed the MS print engine.
Failing that, they could try the PCL driver, which will usually output better from programs that don't handle color properly in the first place.
You could try setting Color correction to LCD display, (or sRGB display) but that will affect all jobs including the ones that were designed for print (and not in a good way)
