One thing about hi-viz is oversaturation, there is so much of it about now it's losing its impact. In particular, yellow hi viz is often worn by slow moving road users (cyclists, horse riders, pedestrians) so people associate it with something going slowly.
As well as something visible, you need to give people something unexpected to snap them out of their daydream (there are good reasons people don't "see" something unless it's unexpected, the brain doesn't pay as much attention as you'd think). This video is interesting:
https://youtu.be/x94PGgYKHQ0
Wearing a colour that is NOT yellow is a decent plan. Orange hi-viz actually works best in low light/overcast conditions anyway because it reflects blue/green light back as orange. Suffers less from oversaturation but still associated with slow moving objects (road workers wear orange hi-viz).
The inevitable conclusion is we should wear pink hi-viz. However, it's hard to find it in my size and robust enough to stand up to high speed riding.
Sadly, I think daytime headlights are also now suffering from oversaturation with all new cars having daytime running lights. The effect of a motorcycle headlight becoming masked in a background field of car headlights is well documented. If everyone has them, no-one may as well have them.
We have one thing left which is movement. We can position ourselves to be seen. Also cars can't move sideways much in the lane. A slight weave on the approach to a junction creates a movement a car can't do and people aren't used to seeing. Our hunters brain immediately notices it and draws our attention to it.
