Neat little thing I just noticed, might be known but I never head of it before: apparently, a Wayland window can vsync to at least 3 monitors with different refresh rates at the same time.
I have 3 monitors, at 60 Hz, 144 Hz, and 60 Hz from left to right. I was using glxgears to test something, and noticed when I put the window between the monitors, it'll sync to a weird refresh rate of about 193 fps. I stretched it to span all 3 monitors, and it locked at about 243 fps. It seems to oscillate between 242.5 and 243.5 gradually back and forth. So apparently, it's mixing the vsync signals together and ensuring every monitor's got a fresh frame while sharing frames when the vsyncs line up.
I knew Wayland was big on "every frame is perfect", but I didn't expect that to work even across 3 monitors at once! We've come a long, long way in the graphics stack. I expected it to sync to the 144Hz monitor and just tear or hiccup on the other ones.
Post the Hyprland config too?
Does it make the entire screen green by chance, not just the windows? If the shader applies to the whole screen, then setting alpha on it doesn't really makes sense and is probably discarded since your monitor can't display transparency. You need to make sure it applies on a per-window basis for them to be composited as transparent and show your wallpaper behind it.