Are you using the global Search (in the sidebar) or search within one note (Cmd/Ctrl + f) here?
Either way, the highlighted search result(s) color can be changed by a theme or CSS snippet. I’d investigate there to see if something is interfering.
The troubleshooting steps are in the template, but I’ll link them again here:
https://forum.obsidian.md/t/about-the-bug-reports-category/24/11