Consider this

[silverside]

I'm just picking a number. 80%. Now... if 80% of the time a crappie feeds up in the water column then why does a lure have a bottom AND top color scheme. If the back is hidden by the belly it could be that the back does not even to be painted with the same results. (I know the lures with front and back colors present 2 different colors at once)

I was waiting for my wife to have x-rays today and this popped into my challenged brain.

[parratt1]

In my estimation, 81% of lures and color combos are made to catch fishermen, not fish...

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[CrappiePappy]

In the "small fish" world the belly is light colored so it's harder to see against the sky/clouds and darker on top so it's harder to see against the darkness below or the bottom. Nature's camo, as it were.
Now, in your question, you're assuming that the fish is directly beneath the "lure" and the lighter color should camo that lure (same as the baitfish they'd normally be looking for) and there's no real need for the lure to have the darker topside. BUT, even though the lure has a lighter color on the bottom, the profile of the lure is still somewhat visible against the sky or the water's surface and also there's vibrations it gives off moving thru the water.
Then you might ask .... well, why do they hit a solid colored bait ?? I would say its profile, speed, motion, scent, or even the curiosity of the fish might be the key to that fish hitting a bait of a solid color, unnatural color, or one that doesn't necessarily "look" like their normal prey (having a light bottom/dark back coloration).
Fish are not geniuses, but they can be picky at times about what they eat. That's usually "conditions" oriented & not color pattern oriented. IMHO

[Les Young]

According to what I see on livescope the crappie swims over to look first & then turns up if interested in eating it. If I’m extremely clear water some do throw clear baits with only glitter in them too so may not be that big of a deal

[Ketchn]

mimicking the darker back and lighter belly typical natural coloration is the key here .
does it matter as many suggest it don't , maybe ,maybe not is what I think .
it so often depends on the moods of the fish it seems to me

[BuckeyeCrappie]

[SuperDave336]

Like we say about bait color in general, It matters when it matters....

[Brag]

I think it's generally to attract the fisherman more than the fish. The average Crappie soft plastic that I use does have both colors fairly visible (top and bottom), but I often wonder about trout nymphs and why it's popular to make flashback type tops of nymphs that probably aren't terribly visible to the fish most of the time.

[silverside]

Here's another way to look at my wonderment...

If you hold a cheeseburger 3 ft over my head I can that it has a nice golden brown bottom bun. But does it have a top bun? What color is it if it does? Don't really know because I'm looking up at it. Is that what a crappie thinks?

[CrappiePappy]

Here's another way to look at my wonderment...

If you hold a cheeseburger 3 ft over my head I can that it has a nice golden brown bottom bun. But does it have a top bun? What color is it if it does? Don't really know because I'm looking up at it. Is that what a crappie thinks?

Again ... you're holding the "bait" directly overhead, which (as you say) shows you the circular outline & color. BUT, if you hold that burger (bait) out from your eyes at say a 45-60* angle, you're likely to see that it does have a top bun (& probably see the burger & cheese showing out the side).

I think Crappie are gonna take the profile into account if the lure is directly overhead, moreso than the colors. But if the Crappie is a little skeptical about that lure, it may rise up to check it out a little closer or it may just ignore it (until it invades its space) or it may flee.

And remember .... it would take quite a long time to drop a jig down to a fish and have that jig stay perfectly horizontal all the way down. Otherwise the jig is going to be diving down head first (lead head first) and the plastic body will be showing its sides ... so the fish will be able to see both top and bottom colors. Unless, of course, you drop it right towards the fish's head, in which case the fish would likely move out of the way in order to not get bonked on its noggin.