WTT for sure I would think, but great looking full helmet aro!
When you say WTT for sure Neil, are you referring to the shine/crossing level or the currently lighter coloration of the fish being due to WTT, or both? For myself I was referring to shine/crossing level, which I personally believe is more genetic related -- that fish didn't get a full helmet like that, and at that age just because it was in WTT for a few months.
Yes, when changing out from WTT to darker background for sure the fish will also become darker/golder, but this is mostly an unavoidable environmental response imo as the fish naturally want to blend in better (though how gold it eventually becomes will still be influenced by genetics).
But again I'm of the opinion that while WTT "may" enhance shine/crossing level (and will certainly make it a lighter overall color), changing from WTT to darker background will not make the shine/crossing go away (if a fish also has good genetics).
I am not gonna put any fish through such treatment, I can't imagine living in blinding white conditions
Each to his own of course, but again that's almost assuredly what the fish has grown up with so far, though certainly no reason to continue it yourself if not inclined.
While this thinking also did enter into my decision to stop WTT, truth be told my fish's behavior or apparent 'happiness level' did not change one iota as far as I could tell after or since making the transition to blue backgrounds. For the record I will also add that my GHXB is much more robust and no health issues whatsoever compared to my BBXB, which I have never kept in WTT (only black bottom and dark purple background), but this could very much be down to chance/coincidence (I'm certainly not going to say WTT helped my GHXB be healthy/strong, but it's still the fact that this is the case, despite the "stress" of having lived in WTT for first ~year of his life).
But taking the whole question of WTT farther one could say similar about bare bottom tanks in general -- many people can't imagine these majestic fish (or others) living in such boring, unnatural conditions. It's a slippery slope argument to be sure.