Unfortunately the tool has no effect for me. I followed the installation instructions, use a custom accent color with the Breeze Light color scheme and no other global theme, the slideshow wallpaper and only one screen, with Plasma 5.23.4 on Arch. When I run the file from the console, it tells me 'applying accent color'. But the accent color simply doesn't change. What could be going wrong here?

An accent color is generated for every wallpaper, but often it does not really seem to match. With many wallpapers I get a kind of blue-green, even though the wallpaper doesn't really contain any green at all; something likes this with lighter and darker variations:

(The window outline is the accent color; the rest of the wallpaper looks the same as in the snippet.)

For some wallpaper the generated color looks matching though.

Is there perhaps some color information from previous wallpapers somehow getting mixed in with the new wallpaper, or the picture not processed entirely? A cache issue on my end?

Or is this intended in order to provide contrast?