Stool (feces) is most commonly brown in color, and many people become curious or concerned when the color of their stool changes. Most stool-to-stool changes in color have little meaning; however, some changes, particularly if the changes are consistent from stool-to-stool and not present in only one stool, can be important.
Could it be anxiety, yes. Could it be something else, I do not know so please do follow up with your Dr. when he is available. Meanwhile as you have so sx of bleeding it may just be the bug you have that is causing the changes in your stool color.