Richard
Hi! Here is your friendly chemist to save the day. Magnesium and calcium, if you look on a periodic table, are both alkiline earth elements. Also, even though a water quality lab (such as mine, and others with more sophisticated equipment that I have worked with) report hardness as either % or per parts per million (ppm) CaCO3. But, that is just to simplify things, in actuality you have other forms of calcium, and magnesium.
Back to your problem, i doubt that the color is from some contamination from an outside source. more likely is a gasket or a washer is being eroded into your system, but for that you need a licensed plumber to figure out from where you are getting it, not a lowly chemist 
A good way to check if your water softener is on the blitz is to turn it on your shower, and see if it sprays all over. If so, remove the shower head, place it in a bowl of vinegar (vinegar is 15% acetic acid by volume, and will dissolve the calcium/magnesium deposits). Let it sit for an hour or so, then put it back. If it works, your problem is indeed magnesium/calcium deposits. as for the sulfur, you need a plumber to determine which filtration system is best for you, but any such system MUST be maintained or its worse than having no filter. I don’t know what region of the country you are from, but if your water smells a little “fishy” you have amines, which is common runoff from farms.
I hope this helps
Rich
[Edited by Richard on 11 November 2000]
