Does anyone know how to prevent this? It doesn't lose as much colour if I just screenshot it. But even the screenshot on the left is still slightly more muted than the original photo. I appreciate you taking time to respond. If you can't or don't know what this is, that's okay too.
Colorspace issues, surely.
Your Goblincore post also looks grey on my machine, so it's probably server-side.
You could try copy-pasting into another program, saving it from there, and crossing your fingers.