[digi_owl]

I would not call it shame, more that society does not take it seriously. I have often mused that if my mental issues had turned my skin bright blue or similar i would get a whole lot more sympathy.

Just try it, wrap a bandaid around your otherwise functioning arm (so its visible) and watch people become more helpful.

[eivarv]

I think it's more about society more easily understanding and thus being able to sympathize with physical pain and disability rather than the visibility of it itself.

Stigma is, after all, more about stereotypes and misinformation (or lacking information) than anything else.

If mental illness also affected skin hue, mental illness might just become more readily identifiable, and (some) people might just be bigoted against blue people instead.