Hierarchy V2 search lens button highlight is dark on light theme and barely visible on dark theme when hovering mouse cursor over it

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Enable Hierarchy V2 (Unity > Settings > General > Use new Hierarchy window)
3. Hover mouse cursor over the search lens button in the Search bar of Hierarchy V2
4. Observe the search lens button

Actual results: On light theme the highlight is fully black, and the same on the dark theme making it not visible

Expected results: On light theme the highlight is not fully black, but grey or some other less dark color, and on dark theme the highlight is visible

Reproducible with versions: 6000.3.0a6, 6000.3.0b2

Can’t test with versions: 2022.3.66f1, 6000.0.58f1, 6000.1.16f1, 6000.2.5f1 (feature doesn't exist)

Tested on (OS): Ubuntu 24.04, macOS Silicon Sequoia 15.6.1