Geoff,
The reality of dealing with dye stains is that the vast majority do not come out, at least not 100% and as we all know, if YOU caused the problem the customer will want it 100% gone, not just faded down. It's not the same when it has a different cause, like the result of a flood etc where there is no blame to attach. As has already been pointed out trying different things in the hope of getting the stains out can make matters worse, not better, the perils of that have already been mentioned by others.
Nigel Woodhead is easily one of the most skilled in this area as he seems to deal with this kind of scenario of a regular basis, but some of the remedies involve risky procedures that certainly aren't for the faint hearted and acquiring Nigel's level of skill is a distant prospect for most and so avoiding situations like this in the first place is certainly how I go about dealing with it because there doesn't seem to be an easy, or reliable fix.
Simon