Since you say that only NEW photos are showing the color shift, it sounds to me that you, somehow, have activated the "Labels" feature for those items which are appearing off-colored. OS-X v10.3 brought back the "Labels" feature from the older OSes. I know that if it were a monitor problem, the color shift would be appearing ALL OVER and not just on certain items. Your menu bar, desktop icons, everything, would be color shifted. That said, I suggest doing a "Get Info" on the items that show the color shift and check their label status.