Gauvins, as car drivers, I figure that we all are aware of how we notice lighter and brighter colours on cyclists from far off compared to all dark colours. I've ridden lots with dark jerseys but at the same time, I've always liked having my rear orange panniers and my bright yellow rackpack on top of the panniers.
I also found and tied a bright red piece of felt to the rack pack handles, and like how it moves back and forth up against the yellow, thinking that it will help attract a drivers eye.

I figure a good triangle on your left pannier will always help.

I've never really used lights in the daytime, but am certain that eye catching lighter colours and shapes on the bike will always help in the situations like shown above--murky lighting, or "shadow / sun, shadow / sun " especially in a corner where a drivers eyes are used to bright sun and they are wearing dark sunglasses and their vision hasnt adjusted to shade---to me, this last situation is the most "real life" dangerous situation--and where I am on high alert and using my mirror in advance and being very situationally aware of what is going on and watching a cars behaviour (and a strong reason why I prefer my helmet mounted mirror)