I honestly don't know, but many Asian aro keepers certainly think that one can "tan" red colored aros using full spectrum lighting.
Do you think full spectrum lights will make any difference? That's really cool about the algae. I use spirulina for blue phyo-whatevers.

The main determining factor in color is genetic potential(just like in humans) , everything else is secondary...
I would agree with your statements to a point. I just think it is a wait of time/resources trying to make a orange fish, red.Correct, but tweaking the other factors that can enhance the color of a fish, can result in a great deal of difference in how those genetics ultimately display themselves. Diet, lighting, substrate color, background color, stress levels, etc, can all have a major impact on the color of most tropical fish.
Looks great! He won't turn red but with proper diet and care he could intensify more in the orange spectrum.
I have seen nicer, but seeing you live in the uk its hard to know if your going to find better, they literally fish these things out of the florida channels in the US so I have see much better looking specimens, I have owned a albino and super orange midus that had bigger koks than this one... So yeah you may be limited to what you can find in your location.