Ok, so, Christmas is approaching (!!) and I am considering some additional lens to buy.

And, I was just curious to know what's the story with Canon's green circled lens: Canon EF 70-300mm f/4.5-5.6 DO IS USM .

I am not really considering that, actually, as I am looking more into wide angle ones (16-35 would be the ideal choice, but it is very expensive. 10-22 seems great and more affordable), or some Macro lens, but still, I am curious on what's the story with the 70-300 "green".
What is the meaning of the Green versus the Red for the "L" series, if there's any?