I have never used an internet coupon, and may never. However, it seems most internet coupons say "void if photocopied," or the equivalent.

Therefore, if they are going to cast suspicion and turn away coupons simply because they are B&W, it should say right on the coupon that only color coupons are valid.

As you say, there are color copiers, and this whole internet coupon thing sounds rife for "coupon fraud" if they are worried about copies.

By the way - there is no need to feel like a criminal if you did nothing wrong. Just stand your ground and hold your head high - there is no need to be embarrassed or feel less of a person than anyone else.