Since the BBC was so rude as to delete my comment on this article, I’ll include it here:
You have this story completely wrong.
The GM tomatoes from a snapdragon gene are BLUE not purple. Purple tomatoes, sometimes called black or brown, are like your picture. BLUE tomatoes are something different and new, and are … BLUE.
There are also a number of non-GM versions of the BLUE tomato. For example here:
http://www.tomwagnerseeds.com/index.php/tomato-collections/blue-tomatoes.html
I might add the picture in this article is probably also wrong.
There’s no reason to eat GM foods, if you want the nutritional value of blue tomatoes. You do however have to grow them yourself, because they aren’t available commercially!