Steps to reproduce:
# Create/open any project
# Click Window  - Search - New Window
# Click a discete next to the search input 
# Observe the background of the menu
# Click Window - Search - Transient Window
# Click a discete next to the search input 
# Observe the background of the menu

Expected Result: Backgrounds should be the same.

Actual Result:  Backgrounds are different. The screenshot is added in the "Attachments" section.

Reproducible with: 2023.3.0b1.

Not Reproducible with: 2023.2.3f1, 2023.3.0a19.

Note: Light mode should be used.