Well, the answer is that they do not have good customer service. AFter my two emails to customer service were unanswered, I called today and discussed the problem. They said they have had a number of calls about the same thing--black stains on multiple areas of the fabric and bleach splatter marks (one cut has an area in the "dark" area where there was obviously a piece of twine on the fabric so that spot is light--in a curved shape). They said that this is not a defective product and is not subject to return postage reimbursement. I spoke to a supervisor and got the same answer. Even though they know quite clearly that there are black stains and very errant coloration problems, they say this is a perfectly good fabric. They offer for me to return it for a full refund but that I will have to pay postage to do so.
This is an unacceptable outcome to me. I have never been so disappointed in a company's customer service before.