KB's comment struck a chord with me. You had to have a color printer in order to use the coupon? A black-and-white printout was viewed as a photocopy? I can understand the company not wanting people to reproduce coupons in mass amounts, but surely a standard printout should be acceptable, especially if the offer is made online. I, for one, use a black-and-white printer almost exclusively.
In fact, I had the same experience at the post office not long ago. I'd downloaded a form from the USPS's Web site rather than getting it at the post office, and the clerk almost didn't accept it. "We've been told not to take copies," he said. Luckily, a printout was OK.
Otherwise, why offer forms and coupons for download and printing online?