Should I tell my coworkers to use the dishes?

I work in an office and am a pretty quiet person. I am environmentally conscious and have noticed that a good number of my coworkers use many styrofoam cups a day for their coffee, when we have a lot of mugs in the cabinets. I don't ever force my ideas upon others, but this wastefulness distresses me. How can I get this message across (and save the company some money on supplies)?