Is there any way to disable the color cartridge in my HP 930c? I want to print only in black.

Under your printer preferences there is a way to print gray scale. SO even if your image is in color, it will print black and white. Every printer interface is different, but when you go to print, there's usually a properties or setting button that will bring you to another page from the initial print menu. here is where you would choose gray scale.

If you try for black with only a color cartridge, it'll come out a dark green or blue color. Or on some cases, it will tell you it's out of black and you can't print. Most HP printers need at both cartridges in the printer for it to print.