I was looking at my screenshots in my modpack with this mod and for some reason I noticed the sun and lamps showing ugly gray-like patterns instead of their true color.
When opening the pictures externally, they show normal values.

I don't know if it's your mod or the way Java works in there, but maybe you got an idea what to do? (HSV/HSL color room or sRGB versus RGB? I don't know much about this topic...)
Modlist see here: xFirefalconx/Royal-Equines-Petrified-Magic#24 (this is not fully accurate, but I last ran these mods when the issue showed up.)

1. Picture in-game:
   

2. Normal comparison out of game:
   

3. Picture in-game:
   

4. Normal comparison out of game:
   

Figured out the reason! Was nerfed by DarkModeEverywhere mod.
How to fix: Go to the DarkModeEverywhere configs and enable the debug logs in the log. Go to the screenshot menu and copy the io.github.lgatodu47.screenshot_viewer.screens.ScreenshotWidget:render and io.github.lgatodu47.screenshot_viewer.screens.EnlargedScreenshotScreen:m_6305_ and paste that to the blacklist, press save, done.

Closing because this mod was not the cause.