After an update I noticed discover was this weird yellow color, I opened settings and noticed it too was yellow, thinking it was some bug, I restarted PC, now everything is yellow. I tried inverting colors but that is something completely different. I'm not even sure what was updated to cause this.
This looks like one of the color blindness filters got activated. Here on Plasma 6, it's a Desktop Effect in the System Settings. Not quite sure, if that was also already the case in Plasma 5, but if you just type "blind" into the search bar of the System Settings, then it should show up and you can disable it.
No option on plasma 5 that I could find, I learned that it was a graphics driver that updated and caused all this, thankfully I had automatic backups setup.
Your colors are inverted.
The accessibility icon never follows accent color, and firewall is always red not blue.
Something is swapping your colors around.
Maybe color correction for the color blind?
Your message actually helped me find a post of mint forums who had the same problem the day before it happened to me, was a graphics driver from oibaf ppa.
My background isn't yellow, it's mountains with a blue sky.
I believe this might be an issue with an app called redshift that automatically comes with mint, it uses geoclue2 which relies on Mozilla Location Service which got shut down like 2 weeks ago. Maybe it malfunctioned that even uninstalling it doesn't help
New plasma update sets the accent colour from your background. To change it go to System Settings > Colours and Themes > Colours (not sure if Mint has it in the same place) then set the accent colour you like from the top.
Oh I see, that is odd. I thought your background was yellow beforehand. Is it perhaps plasma's Night Light? That will tint everything yellow when it's enabled.
Was yellow with x11 plasma and cinnamon except cinnamon on Wayland was normal, I tried switching to lightdm and it was giving me errors.
I found someone had same issue a day before on mint forums. Apparently it was a graphics driver from oibaf ppa.
I forgot I had timeshift setup monthly (changed it to weekly), so I restored it and everything looks fine. I didn't lose anything because I was so busy that I only had energy to played Factorio after work which are steam cloud synced.
Didn't try different user (since i don't have any other), it was on boot menu and both x11 cinnamon and kde plasma, wasn't on the experimental cinnamon on Wayland tho.