I added a print line to a python script while the script was executing, and now all the text is highlighted in red when I open the file. Opening and closing the file doesn't get rid of it. Opening a second python file momentarily fixed the problem, but then closing file and reopening brought the problem back. Now it wont go away at all. Any body know what could cause this?
Old thread, but hope this helps.
By mistake I did a "/." on my vim screen, which highlighted all lines in red. If I open any other file, the red highlighting stays. 
Try searching for some other keyword, let's say "/word" - doesn't matter word exists or not. It restores the color.
vim highlighting everything in red