Your eyes work on contrast - which is why a dark object stands out perfectly well against a light background. Road surfaces appear pale grey in the sun, so someone wearing black will be perfectly visible. On the other hand, hi-viz appears the same dirty orange as the road under the streetlights. If you think that it makes you more visible after dark, you're deluding yourself. I usually spot hi-viz cyclists at night by the shadows they cast under the streetlights, because what they're wearing blends wonderfully well into the background.
You do, I trust, manage to spot and avoid all those black cars, don't you?