Sounds like Bile for the green liquid? I've done cleanses on my period, I think it's a great time to do it because for one, You already a slave to the toilet, well at least I am when on my period and I like to stay home for the first 2 or 3 days. Your period is your bodys way of cleansing the blood stream of excess toxins, Some say the ancients never got their period because they never had excess toxins in the body. The dark rings sounds like aliminium? Possibly from pots or pans you use? Or a cup or container? Or eating out somewhere that uses these?