This is what I think.
Specifically for floater baits here, pretty much all of these baits mentioned are white on the belly anyway.
Its a term referred to as countershading. Pretty much every fish that exists has a countershaded pattern. Lets take a great white shark for example. Deep blue tint top with a very specific line that turns to white. This is so for another predator above them in the water column looking down, they blend better with the rest of the ocean around them, allowing them to stay unnoticed. Then a fish or predator below them in the water column looking up sees a white belly compared to a bright sky. Again hiding the fish.
Well with the floating baits, at least in most cases have a white or slightly silver-ish belly, right?
From pool tests Ive done, if you place them in the water, what part of them is usually above the water line? The colored part leaving the white to all the submerged views. Again Im clarifying for floater baits here.
IMO it doesnt matter whether your bait is solid white, kokanee, green trout, or pink on top, because what is the fish seeing? The white belly.
What is really boils down to is what gives you the most confidence to keep a bait tied onto your rod and in the water. So the reason so many fish are being caught on all white baits really comes down to people believing them and so they keep throwing that bait instead of another.
This is just my opinion. Anyone else feel free to correct me.
Justin