In practice, research and experimentation is done to work out the right combinations of light colour for the particular sort of fish you are trying to catch, an

In practice, research and experimentation is done to work out the right combinations of light colour for the particular sort of fish you are trying to catch, and then fixed light sources are built for that. In some cases the roll-off from colours you want to colours you don't is quite sharp and that's easier with fixed illuminators rather than RGB. Edit: I have a clearer way of explaining the challenge. We are used to 'any colour' being possible from RGB style LEDs. That is one resolved colour that we perceived. But for this we aren't trying to achieve one colour, we are trying to configure a particular spectral output. You could maybe get close to that with lots of LEDs across the spectrum, but it's not the same as well designed cluster.