Low contrast shading is not visible under normal usage. Light grey and white are shown as the same color (white). If I producing a shading effect (i.e, by dragging another window's shadow or doing a screen capture), the previously invisible light grey is visible.
This happens on one user account, but not others. I have the same issue on my MacBook Air (2011) with the same user account.
Any ideas what might be running with this user that could cause this?