Ah, but the defense from light intensity by producing pigmentation is what we're (generally) hoping to acheive in our coral gardens. Natural, in this case, can be somewhat subjective. If the same coral is found at 6' of depth and 25' of depth, I would expect the colours to be different yet both still "natural aka healthy."
Frags of this coral that I have given away to others, some with bluer lights, and some with just more intense lights, the coral just turned fluorescent yellow. In the case of this coral, I beleive the purple is in fact the natural colour, and yellow is the "ok this is too much" mechanism, and brown is just ... well it's not unhealthy but it's not very pretty to look at, either. Purple is how it's been for me for 4 years prior to last year when I moved it into my "SPS tank." Previously I had grown 1/2" frags of it to 10" monsters of it. It grows like a total weed under 10k's. 10K's appears to be the best light for this one. Just my observation.
I'm not completely disagreeing with you here.. I agree with everything else you said. I'm just asserting my own opinion that colour temperature is not wholly irrelevant. Like with other things, it plays a role. Whether that role would be "small" or "substantial" is perhaps open to debate, but all I really want to assert is it's "non-zero."
BTW, I'm not looking for Radiums to be a colourworld, I just want to try them for my own viewing pleasure. I can't form an opinion on lights until I've tried them for at least 6-12 months.
I've tried several different combos and my personal favourite, of what I've tried that is, is still the 10k's. But I want a share of the radium pie too (so that I can form my own opinion)! You guys get all the cool toys, and then pooh-pooh the rest of us when we try to jump on the bandwagon. That ain't fair!!!
PS. OTOH, I certainly don't disagree that people get far too hung up on colour temperature. There isn't, IMO, one all-encompassing light temperature, the "OneTrueLightTemperature(tm)." The trick is to find what you like, and work with it. Some things just respond differently to different things, so you find what you have, find out how it responds, then run with the one that seems to give the results that make you happiest. For some it's 6500K's, some 10K's, some 12K's, and some Radiums. By no means am I putting Radiums over all my tanks .... I have no desire to change away from 10K's over my anemone tanks, for example. Very happy with the results there.