There is no right answer to your question. Well, maybe "It depends." is a good answer. It depends on what kind of lights you have, especially what kind of PAR they are generating, how deep your tank is, the kinds of corals you keep (you did that one), how clean your water is...
I have 200 leds (480W) and generate 200+ PAR at the sand in my 180g sps & lps DT. Until yesterday I was doing a 4 hour sunrise, 5 hours of midday ate 90& blue and 50% white, and the a 5 hour sunset that got more blue as the sunset progressed. But I just changed it to a 7 hour sunrise from slightly blue to white at midday (100% on both for an hour) and then a 9 hour sunset that slowly gets more and more blue until the last 2 hours of 30% blue and 20% blue with no whites at all.
If you just have dimmers I'd suggest a 1 or 2 hour blue only for sunrise and sunset and anywhere from 6 to 10 hours of both. But it really isn't all that critical IMHO. Corals only get 4 to 6 hours of really strong sun (2 or 3 hours either side of high noon). Before and after that, the sun's strength is reduced and at any real depth it's reduced even more.
