DPM - Difference between Black and Blue

[sotal]

Quick easy question what is the difference between Blue and Black DPM?

Blue = £13.55
http://www.screwfix.com/p/damp-proof-membrane-1000ga-3m-x-4m/12666


Black = £8.35
http://www.screwfix.com/p/black-membrane-1000ga-3m-x-4m/50464



Both the same size, both the same thickness but the black is over £5 cheaper. Any reason?

Thanks

 

[sotal]

Found the answer via the similar threads at the bottom:

http://www.diynot.com/forums/viewtopic.php?t=189986


I'll get some black then!