It is not just a morph thing. Your light plays two roles... first, it develops diatoms in the coral that use light at one spectrum and then spit it back out at a higher spectrum - these can shift over time. Second, those same diatoms reflect back light exactly how it was emitted from the coral - this is immediate. Even though the diatoms might still be there from before they were shipped, they can only reflect what light you have. If you don't have the same spectrum to get reflected, then the color will be different and oftentimes less. This is why full spectrum light sources look so much better to most people - I mean real full spectrum, not LED full spectrum that still have many, many spectrum holes.
Here is what I think happens in these case... which is hardly scientific. 20K radium, 14K phoenix and other MH bulbs produce generous amounts of actual UV (not violet that LED manufactures call UV), which is used by the diatoms below 400nm and spit back out just above where we can see it. This will provide color that no LED can match and just a few T5 bulbs since the input spectrum was below 400nm. This is why blue and purples pop so much more under MH... not fakeish reefbrite pop like the corals are living in Windex, but actual pop with the crisp white appearance.
...and then there is Photoshop. This seems taboo to talk about on the internet anymore and will get you banned from R2R, but even some of the vendors around here to WAY TOO FAR by altering their photos. Those photos look pretty greasy.