Royal blue (453nm) and Actinic/Violet (420nm) are extremely important for corals, much more than the red spectrum. In the ocean, red light is filtered out quickly (past 30' you would be hard pressed to see any red), and corals don't have a good built in mechanism for dealing with 'too much red' like they do for the blue spectrum. Think of the blue and red as batteries. In corals, blue light can fill up the blue battery, and if it gets to much blue, it can spill over into the red battery for extra storage. With red, that isn't the case, if you fill up the red battery, once it overflows, it just causes damage to corals (plants don't react this way). This is because corals do not get much red spectrum and over the eons have either lost the ability to regulate the red spectrum or never had that ability to begin with.
Beyond spectrum though, you have to meet a proper intensity for the light. Dimming the light down to get a good personal preference may in fact cause the light intensity to drop so low it can't support photosynthesis. Think of it like cooking a piece of meat with a match vs a grill, no matter how many matches to light, you are going to be hard pressed to ever get a slab of meat to cook properly. This is where the 'balance' comes in between personal preference and usefulness. As an example, you could make a light that is 3:1 ratio of Warm White to Royal blue, but then you would have to turn down the whites to around 15% tops in order to give you a personal preference you like, which cuts out 85% of the intensity, which is bad. So you want to design a light that comes close to your personal preference and use the channels to fine tune the color while also maintaining a good intensity. Most people now are going with around a 1:2:1 ratio of Violet/Royal Blue/Warm White.
Beyond spectrum though, you have to meet a proper intensity for the light. Dimming the light down to get a good personal preference may in fact cause the light intensity to drop so low it can't support photosynthesis. Think of it like cooking a piece of meat with a match vs a grill, no matter how many matches to light, you are going to be hard pressed to ever get a slab of meat to cook properly. This is where the 'balance' comes in between personal preference and usefulness. As an example, you could make a light that is 3:1 ratio of Warm White to Royal blue, but then you would have to turn down the whites to around 15% tops in order to give you a personal preference you like, which cuts out 85% of the intensity, which is bad. So you want to design a light that comes close to your personal preference and use the channels to fine tune the color while also maintaining a good intensity. Most people now are going with around a 1:2:1 ratio of Violet/Royal Blue/Warm White.
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