I personally like the all-in-one printers from HP, which tend to be just at $100. But they have reformulated their new ones to use cheaper ink. Also, you might look into buying one online if you want it cheaper. I got the HP Photosmart 4200 all in one for $40 on ebay, and it works great for color and b&w.
The other thing about ink is that some places, like Walgreens, will refill your old cartridge for cheap. I think b&w is $10 and color is $15.
It's definitely an advantage to have color when printing powerpoints for class since some professors like to use background colors that blend with font colors when in b&w, or like Nexx said, with certain photos.