Hi!
Welcome to the MedHelp forum!
If the stool is not floating, then it should not be the cause of concern. Darker stool can be due to more rapid transit or due to having more starch. However if you are having gas or constipation or foul smell in stool, then it needs investigation. Otherwise forget about it.
Hope this helps. It is difficult to comment beyond this at this stage. Please let me know if there is any thing else and do keep me posted. Take care!