Why would half of your bowel movement be darker than the other?

Consider this...: Although much of stool is the bacterial flora of your gut, what you eat plays a big role in gut motility, effectiveness of digestion, stool pattern/appearance. Fiber supplements increase bulk & therefore stool volume. Adequate fluids avoid dessicated stool. Stool color is very dependent on ingestants.Also, diet modification, exercise, bleeding changes food transit time & the resulting stool.