I'm far from an expert on lighting and I'm not exactly sure how this user came up with this, but I'm guessing it's a combination of spectrum and color preference. On the spectrum bit, the 420-470 range is one of the most beneficial for coral, so that combined with the blues and UVs bringing out the flourescence of coral and making it more visually appealing is the main reason most people have their blues so high up. It makes the colors pop and is great for coral health.
On greens, only a small piece of the spectrum is useful to coral and it's mostly to help blend other colors, so most people don't have their greens up. On reds, I believe it helps the coral determine it's depth, but isn't crucial for coral health. Whites are good for growth and health, but aren't as visually appealing, so that's why you typically see a lot more white than green/red, but much less than the blues.
The last bit of the equation is the final spectrum you're lighting the tank with, which changes slightly with the adjustment of every single color. So when the blues are jacked up, it hits that sweet spot well, but that slightly changes (either for the better or worse, in regards to the total spectrum) as you adjust other channels. Long story short, having high spikes in the 450 and 600 range is pretty much universally considered to be the most beneficial spectrum for coral growth, health, and color. So generally, people will try to make their setup as close to that as possible, while also being visually appealing.
I'll say again that I'm far from an expert on lighting, so someone may have to correct some of what I said, but that's the general gist of it.
