Color Profile change when Dummy is mirrored

[linjie0928]

I am a professional user and need to customize the color profile, but there will be some differences when the dummy is enabled.

[waydabber]

Yes, I noticed this one as well.

• If you don't have a mirrored Dummy, then the Color Profile selected under the display in Displays will apply.
• If you enable mirroring from the Dummy, a combination of the Color Profile selected under the display and the Color Profile selected under the Dummy seems to apply.

The color profile defines the tristimulus color space information and the white point for each display. If the two color profiles don't match, macOS seems to apply both, to find a middle ground.

Dummies have the same color profile as Apple's "Generic RGB Profile" (you can check this in ColorSync utility) which is fine for 99% of the users.

To fix this issue, you might need to experiment with Color Profiles and create a custom profile that works. I'd say the first thing to try is to set the same color profile both for the physical display and the Dummy, but this is not always guaranteed to work as it seems (at least in case of some profiles, but seemingly not in case of some others) that the profiles are applied in a strange, cumulative fashion.

I plan to experiment with this more as well when I get to it.