Can tertiarySystemFillColor layer of _UISearchBarSearchContainerView be modified?

Question

My question/issue centers around the use of the _UISearchBarSearchContainerView search field component, and the fact that our small team can't quite figure out if it's possible to either remove, hide, or make completely transparent its top-most gray layer (which is set to tertiarySystemFillColor)... labeled #2 (pink highlight) in my screen capture below. This particular top-most gray layer is what we would like removed, hidden, or made completely transparent, because it has a gray Background of R:0.46 G:0.46 B:0.5 A:0.12 (tertiarySystemFillColor) that we do not want seen.

We only want the 25% alpha white layer underneath it to be seen... which is labeled #1 (green highlight) in my other screen capture below, that bottom layer has a white Background of White:1 A:0.25. This bottom layer is the only layer that we want visible as a background for the search input, so that the input is only a 25% alpha white coloring. The top-most gray layer (#2 - tertiarySystemFillColor) sitting above the 25% alpha white layer (#1) muddles the desired pure white background color value with gray.

We think that anything that uses a default iOS component which starts with an "_", such as _UISearchBarSearchContainerView, can't be edited more than it has already been done by us... but, we kind of have to believe that not every search container has to be stuck with that top-most gray layer, muddling the coloring of the layer beneath the top-most gray layer.

Can that top-most gray layer of the _UISearchBarSearchContainerView be removed, hidden, or made completely transparent by giving it an Alpha of 0 (zero), for example? Or some other method?

Thoughts on this? Thank you for your time and sorry if this has a basic answer that we do not know.

Top-most gray layer (#2 - tertiarySystemFillColor) we want removed, hidden, or made completely transparent

Bottom 25% alpha white layer