Kent fire service run a fab (award winning) course (ask Dazza of the photo game fame) for bikers and one of the sections is on hi vis. It's a thought provoking session.
Main points I remember - Hi vis only really works when light is shining on it, therefore, if you are on an unlit road with no cars coming the other way, the driver about to pull out on you has his lights pointing 90 degrees to you and therefore won't light you up.
Think about your surroundings, hi vis vs the dull grey of a city is great. Hi vis (yellow) on a county lane, in autumn when the leaves are yellow, with a low sun will not show up against the background at all.
Hi vis bibs are mostly hidden by fairing looking at the biker from the front. Hi Vis with arms is much better because the arms stick out from the bike.
Dazzle camoflage..... in WW1 they camoflaged boats by painting them losts of colours and shapes in random patterns, this makes it hard for the person viewing the boat to judge distance and direction. If bikers wear lots of different colours (helmet, leathers, boots and colour of bike) this can come into effect for us. We alsmost blend into a drivers vision. It's better to be a solid sillouette, and ALL black actually makes for a damn good sillouette during the day, especially against sun.
just some ideas....