I voted for multi-coloured LEDs, on a timer...I also like potatoes.
I've always been aware that any tank I have, in a normal room, is subject to ambient light and, as such, when daylight gradually breaks, the fish are exposed to the gradual 'enlightenment'.
I was always aware that, in spite of this, when I switched the tank lights on, there was a startling amongst some, not all, of the tank residents. This was even more exaggerated when I had a fish cellar, with no ambient light whatsoever.
The very simple fact that I can have my tanks come on gradually, is a boon.
At the other end of the day, when all lighting is artificial, switching off was equally as abrupt and, from using a red-tinted torch, I was able to see that the fish were as startled by the sudden loss of light, as they were by its sudden and drastic appearance.
So, again, the gradual diminishing of light is welcome.
I'm still learning about spectra and plants and it isn't as simple as some suggest. I also believe that the boffins behind the lighting companies may not be the total crackpots some like to believe...so I continue to explore lighting possibilities.
Currently, not including sunset, (1 hour) and sunrise, (1 hour), my lights are on for 8 hours...with 4 hours 'moonlight' and 10 hours total dark.