I have in administration 2 C500 Pro.
In the first month the machine consumes a yellow tonner/1500 copies
the image was full of yellow
The best profile is
that what you make for this machine!
The machine on default calibration are wery greedy with tonner (eat a loat of tonner) and put on paper a loat of colour( tonner).
If you have a Creo controler the problem was much easier because it came with a spectometer.
So with internal ( or external) fiery you should learn a little to control your profile with ColorWise Pro Tool with alow you to edit profile and to adjust each color!
So my final advise please install "ColorWise Pro Tool" is on the C500 Fiery disk and then play with the soft and then

will should talk...