Despite this being common practice to use green light and there being manufactured green lights designed for dark cycle lighting, I think the idea of 630-730nm red lights to view during dark cycle should be much further investigated since it's been disputed by very few individual growers and also has been said to have beneficial effects on flowering if used early during a dark cycle. There has also been more recent proof that green light during the dark cycle isn't as safe as once though, especially if the plants are exposed for a long period of time. I realize people will insist that green light is safe for dark cycle viewing, and the idea of red light during dark cycle is ridiculous, but generally people are just repeating what they heard and will never do any experimenting or scientific research to prove otherwise. I sure as hell am not going to do the research myself, but I've heard a few times that red light should be used instead of green, and I know that 730nm(UV light) improves flowering if briefly introduced during the dark cycle of flowering. I'm sure it's unlikely that an advocate of red light over green during night dark cycle will ever read this and I understand it being so quickly dismissed as a ridiculous notion.