NFU Scotland was quick to condemn EU proposals announced yesterday to scrap the special tax concession on diesel used by agricultural machinery that allows them to buy  red diesel  at about half the price motorists pay at forecourt pumps.  Currently, those involved in agriculture and fishing in the UK and most EU countries are allowed to use the cheap fuel that is the same as regular diesel except for the red dye that is added to prevent ordinary motorists from using it. That distinctive colour allows police and customs officials to easily detect it  in vehicles that are not exempt, and there are reports that there has been an increase in its illegal use recently as fuel prices soar at the pumps.  The European Commission s proposals look to remove existing tax