Sometimes the image fer the pet or enemies will invert.
As you can see, not all invert an unno whats causin' it.

I think that might be whatever extension you're using to change the site to dark mode.

Can you try disabling that extension and see if the images return to normal?

I dunno how... I have jus been usin' the site as it was.

Sylestia doesn't have a native dark mode. So you are either running a browser extension to override our CSS style sheet or using a browser or device app to fully override your entire screen with a dark mode (I am assuming it's something like this since it's changing the images itself, which is beyond what CSS would do).