I have a canon EOS T4i with stock EF-S 18-135mm f/3.5-5.6 IS STM lens, a Rokinon 35mm f/1.4 Lens, and a Sigma 150-500mm f/5-6.3 DG OS HSM APO lens. I'm trying to photograph the various corals in my reef aquarium which is lighted by 240w LEDs (50/50 white/blue with a few reds). Most are stationary hard corals but some are pulsating and undulating soft corals. A problem that I am having is the lack of vivid, true colors. I'm not sure if my settings are wrong or if a filter is needed in order to get the true colors that are visible with the naked eye.
For really good colors you will not get around buyng a color reference card and lighting it with the exact same light as in the aquarium, maybe even submerging the reference. Take the photos in RAW and the software that the color reference belongs to will calculate a profile for the shooting situation. This profile can then be applied to the real photos and the colors will be correct.
I know it can easily be done in Lightroom (there are plugins from the reference vendors), not so easy in Aperture.
For starters, you can use a grey reference card, make a test shot and adjust the white balance (in Lightroom, Aperture or Photoshop, maybe even the GIMP). This will give you better results but not as good as with a complete color reference.
datacolor is one of the popular vendors of color profiling gear.
The camera sensor has a different response to light as compared to the human eye. And as the light over the acquarium has a different spectral composition from daylight, the sensor gets confused.
It and the camera try to compensate, change the recorded colour balance as if daylight were falling on it, which of course leads to a distorted colour balance on the resulting image.
Setting the camera for a white balance mode for TL light might get you a closer match. A pure white test exposure under that same light can then be used in post processing to get the required post exposure compensation for the actual shots.
The excessive amount of blue light is probably your problem. If the color of light is severely out of proportion, it can cause problems with properly exposing color. Basically, the blue sensitive pixels get over-exposed while the red and green are under-exposed. This can make colors look subdued and weak or make the entire image look tinted and noisy.
You can try shooting RAW to see if there is still enough red and green to get a good exposure, but if not, you will need to change the lighting to have a more even balance of red, green and blue (or just plain white). Also note that some color LEDs behave weirdly with cameras due to not producing the frequencies of light that go through the filters on the pixels.
So the solution would be, first try shooting RAW and trying to adjust the white balance in post, possibly using a submerged color target to help get closer colors. If an initial, simple white balancing attempt doesn't work at least marginally well, then you probably need to get different lighting to allow relatively similar amounts of red, green and blue light to be received by the camera's sensor.