Dr. Tan, welcome to the board!
I agree with you that water management and koi raising skills are the most important factors, and genetics being less.
It is often said that kois imported into Thailand looked their very best when they got off the plane This is true even for the prize-winners with excellent genetics that were specially imported just for the show.
Some ponds with chillers manage to maintain quality of the beni and shiroji, but the kois never look as vibrant as when they had just arrived.
I have gosanke and shiro utsuri in my pond(whose water temperature dropped down to 28.9C last week due to a cold spell). Sumi look good, very shiny on one matured old-style showa. However, the beni on all my showas, sankes, and kohakus does not look very good. They are thick, but not vibrant. Please note that I do not use color-enhancing feeds, and only use wheatgerm(Hai Feng).
I have seen locally bred hi-utsuris that are really eye-catching. The contrast between shiny sumi and bright red hi are something else! These hi-utsuris come from the old genetics and might be more relevant to Mr. Akitaka Kawahata's observations.
(Speaking of ZNA, I am trying to jump start ZNA-activities in Thailand by forming a local chapter. I could not find the contact-information on the net, could someone please give me contact-points for this area?)