Blue lights over reef aquariums.

Just look at nature in the ocean!
First up, in nature the suns colours are best seen in rainbows, once the light goes through the water/rain the hidden colours become obvious!
The reason the ocean looks blue is that the blue part of the suns colour spectrum penetrates the water deeper then any other colour.
Red is relatively the weakest of the suns colours and it is near on gone by 30 feet down in the ocean and is the colour to avoid over a reef tank as it inspires crap algae!
Over external algae, the red coloured diodes can be okay, but its best to stick with standard blue and cool white diodes over algae!
From the colour of the ocean with clear waters and blue skies, you work out that blue in shallow waters actually harms some corals that’s why they fluoresce in the ocean and especially in reef tanks, they reflect the lighting back away from them to preserve their health.
Many folks wrongly think more blue lighting is good, it isn’t!
The right mixture of blue lights along with cool and warm white diodes, the blues turned down is good, do not use full on blues, in time corals are harmed.
Cool white diodes have all colours in its vast spectrum very similar to the sun.

There are colours that do certain things though, green diodes inspire red to pink in corals, but that is more trial and error to find what works best for your needs.
With basic but very affective reef lighting, lights over 15 inch to 2foot in depth should be 80 degree optics and red diodes near off, green is full on as is cyan and blue are at 50 percent and warm whites are 50 percent as well and cool white are 100 percent and if lights are just all on, or off , your corals will do fine, if water is suitable of course!