A plausible explanation for invisibility would be the potion causing a person's bioelectric field to seamlessly bend light around them. This works better than if you were transparent, because then light would pass completely through your body, including your retinas, leaving you blind. Also, the light warping effect would avoid a person's pupils, since your eyes would still need light to pass into them so you could see, and complete light bending would also leave you blind. It's not total invisibility, but it's extremely hard to spot a pair of black dots just floating in the air, and you could minimize those by squinting, or just closing your eyes.
this is getting good
A plausible explanation for invisibility would be the potion causing a person's bioelectric field to seamlessly bend light around them. This works better than if you were transparent, because then light would pass completely through your body, including your retinas, leaving you blind. Also, the light warping effect would avoid a person's pupils, since your eyes would still need light to pass into them so you could see, and complete light bending would also leave you blind. It's not total invisibility, but it's extremely hard to spot a pair of black dots just floating in the air, and you could minimize those by squinting, or just closing your eyes.