Your main drain is clogged and need to have a professional auger it out. The red stuff could indicate a broken drain line. If you live in Georgia where red clay soil is prevalent, I would really suspect that. When the plumber augers the drain, he should be able to determine what that material is. In the meantime, DO NOT pour chemicals into the drain. They won't help the problem and will create a potential hazard for the plumber. If you already have treated the drain with a chemical, tell the plumber when, what, and how much you used for his safety.