Red lite IMHO is useless. I guess idea is that creatures are not scared that much by red light as white.
On day dive you may use flashlight to look into holes but if anything is there it will hide whatever you do unless it is not scared anyway (like moray eel). If you want to take a picture it is better to to have your camera and white light ready pointed away and then aim and try to take a shot.
On night dive you have your flashlight on all the time and you should not turn it off, so suddenly red, not happening. Maybe if you pro underwater photographer with rebreather sitting somewhere underwater waiting for something... Not a regular person.
UV supposed to be for bioluminescence, and it works (depends on coral and creatures) but blue (royal blue) is better in most cases, you need yellow filter for good result so UV is kind of easier but UV is not recommended because it harms coral and fish, should not be used!
So, for diving I have one light that I can switch from spot to flood, use spot and when I want to take a picture I switch to flood. Could have separate light on camera or even more sophisticated setup but for me diving means travel and space is premium. I have a separate blue light and so far I only used it on one dive (I removed dome and phosphor from
Sofirn SD05, since white LED is a blue led with phosphor on it)
