We are trying to prevent employees from using color print when it's not necessary but they are too lazy to change the color setting (change to Black & white print) before printing. So I am trying to figure out how I can automatically keep the black & white print only and apply it to all employees.

Our IT dept tried (installing printer server and change the default Black and white but if you change it to color print, the setting will stay color print unless you change it back to black and white) and kind of gave up...

Does anybody have the same problem at where you work?

If you are so worried about color printing, and the costs involved there's a couple of approaches you could try.
Simply replace all printers with monotone units and have a very few color capable devices that are controlled. Many multifunction copier machines offer control on color printing and are network enabled.
Or the other approach is to monitor everything that is printed and then CHARGE each department for the printing they do each month. Make the cost of printing a departmental rather than central cost..