Colon cancer is rare in people under the age of 40, and not very common in people without a family history.
Black flecks could indicate blood higher up in the GI tract; black in stools is oftentimes linked with bleeding ulcers. But tiny amounts of small flakes doesn't sound like a bleeding ulcer. Actually, it sounds more like something you ate. Kool-aid can turn my stool blood-red, and I seem to recall that someone on here linked something like black flecks to broccoli. Pepto Bismol will also turn stools dark/black.
I wouldn't worry unless these flecks become more numerous, larger, or are accompanied by a black, tar-like substance in your stools.