I bought a new OLED monitor, which worked great with my Windows machine, but when I connected it to my MacBook Air and MacBook Pro via a USB-C to HDMI* adapter the colours all looked very wrong.
Blacks were tinted fuchsia, whites were tinted yellow/green, all colours look wrong, yet the macOS UI is still legible. Turns out the issue is that macOS thinks the monitor is a TV and encodes colours as YPbPr instead of RGB.
There appear to be two fixes:
- For Intel macs, overriding the EDID information via a plist at
/Library/Displays/Contents/Resources/Overrides/DisplayVendorID-$VENDORID/DisplayProductID-$PRODUCTID. There’s a handy patch-edid.rb script for this purpose. It works by setting the
IODisplayEDIDkey in the plist with a base64-encoded EDID payload. While the script clobbers other potentially useful EDID information, it’s a useful starting point.
- For Apple Silicon, overriding the
/Library/Preferences/com.apple.windowserver.displays.plist. See Force-RGB-color-on-M1-Mac for a great description of this method. I haven’t tested it though, because I only have Intel macs.
Figuring out the fix was a bit of a process for me: my first few searches suggested it could be a cable problem, but I verified the cables worked just fine with the same monitor and other computers. It also didn’t look like the typical colour aberrations when you’re just “missing” a colour channel. Then I thought it was a problem with the USB-C to HDMI adapter I was using. When I stumbled on old (2013) blog and forum posts I was initially skeptical that it was the same issue or that the workarounds would still work. But it turns out that it is a macOS bug that’s been around for 10+ years, and the old workarounds still work!
* I know DisplayPort would be better, but I want to leave the monitor’s DisplayPort socket permanently plugged into my PC.