Silver 12,5kg butane gas bottles

Hi all, I am using 12.5kg orange butane gas bottles at the moment, but I'm looking to change over silver butane 12.5kg  bottles.

I'm not sure what the cost difference is from orange to silver bottles when purchasing or refilling?.

I have 2 empty 12.5kg orange butane gas bottles at the moment, but I would like to swap to silver bottles, does any one have any to sell or  swap?

Because going forward I only want to use silver bottles, 

Any advise would be appreciated on any of the above and also on where is the best place to purchase silver butane 12.5kg bottles and the price near El Prado Arboleas.

Cheers Gaz