I have yet to see a yellow yellow plant, except in the picture on the web it does appear yellow. Whether this is what the plant is supposed to look like or whoever called it yellow just happened to have a malnourished green form in blazing sun turn yellow.. beats me. Maybe next year I will toss one of these 'yellow' clones from Australia out in full sun and see what happens..
I'm not really sure where my clone originated from exactly, I believe somewhere in england, but I had it out in full sun for most of the season this year. So far I haven't noticed coloration at all, it's just kind of a pale green. No red, and the only thing yellow like that one picture i've seen that actually looked yellow was a dead or dying leaf.
Maybe I should try one of the Australian clones and see if there's a difference.