Usually the coloured ones are specialised ones to do certain things, like the green one is anti microbial coating, or some have more activated carbon to remove oders from the air better
Ok, well I suppose that makes sense. However, having been involved in manufacturing I know that it's not unknown for companies to do something just to charge more money - without any real benefit for the customer. But, I'll give them the benefit of the doubt. Why not. Thanks for the comment!
