Transparent colours and images are shown in red For a long time I have had an issue with display color—it strangely has more red color in it as I can see. As far as I understand, it is due to how transparency is displayed.

The upper menu bar is having this redness, or in Preview.app for example, when viewing PDF files, it is blinking between normal white color and red background transparent color as you keep scrolling.

I tried to calibrate system color in System Preferences, but without any positive result.

Here are examples when using viewer to read some pdf file:


Here is how all the images are displayed (this redness I tried to explain above):


While scrolling, transparent red layer blinks from normal





This is only an example, It's not an issue only with this app, it's just easy to see it using this app.
Open Terminal and enter:
defaults delete -g CGContextHighlight2xScaledImages and hit the Enter key.

Restart your Mac.


This will disable highlighting non-retina images with a red overlay (probably in Apple apps only).
To reenable it open Terminal and just enter:
defaults write -g CGContextHighlight2xScaledImages YES and hit the Enter key.