I selected the "Wood" theme for a SharePoint site created in SharePoint Online, and noticed that the backgrounds that appear to be transparent in the preview are actually opaque.
Here is the preview. Note the transparent backgrounds on the side menu and main content, and partially transparent top menu:
Now, after selecting the theme and navigating to the main page, I see the following. Observe that the side menu, top bar, and background of the news section are opaque, when I would expect them to be transparent or translucent based on the preview:
Interestingly, the backgrounds appear correct when I navigate to the Site Settings page:
I've tried this in both Chrome and Edge, and have also tried other themes that use transparent backgrounds. The effect is the same on all of them. Any ideas on how to resolve this?