This is the Spectrum Minimal Classic Colors theme locked with the Garnet color scheme so it stays red regardless of the color scheme you are using. Use this if you want your panel and widgets to be red, but to have different colored windows. Contrast issues may be present and folder colors for the desktop are lighter than the color scheme.
This plasma theme is used in Spectrum Garnet
Have you tried turning it off and on again? Sometimes plasma assets will not update and some may still be themed according to something you previously had set. This can usually be fixed by restarting.
To restart just plasmashell, open KRunner with "Alt + F2" to execute the following 2 lines: