Sudden greyscale shift on Macbook Air I think this is a duplicate of an old question without a good answer: Display appears different on two accounts using same color profile
My child was doing schoolwork on her school-issued Macbook Air. Suddenly lighter greys are totally white. This generally gives the images on the screen a vague feeling of being &quot;off&quot;, and pixellates all curved edges. The biggest problem is that text on some of her sites is unreadable.
I've checked the following:

Color profiles - it looked like it was using the default, but a cycled through a few built-ins. I could see noticeable changes to color balance, but the light greys remained the same as white. Also deleted contents of ~/Library/ColorSync/.
Accessibility - my child has accidentally inverted colors before, this isn't that. No other accessibility settings seemed related to color.
Display settings - Modifying brightness was also fruitless. The screen overall got brighter or darker, but still couldn't distinguish between light grey and white
Rebooting - colors look fine until shortly after logging in - seems connected to user profile somehow.

Here are some images to demonstrate the issue. This is a generic color test image:

On the Mac, it looks like this (simulated with photoshop):

Any solution would be appreciated, but if there is a keyboard shortcut that can cause this, it would be the most likely explanation (8 year old says they &quot;might have rested their arms on the keyboard&quot; during a class meeting)
Best guess is Display Contrast.
That will affect the on-screen image, but will not translate to a screenshot. Screenshots are taken before that filter is reached. The on-screen image will be affected similarly to your Photoshopped version. [It will actually compress the blacks a bit too, so not exactly the same as your image.] Almost like putting a really agressive curve on it -

System Prefs &gt; Accessibility &gt; Display. [from Mojave, things may have moved a bit in Big Sur]
Set Display Contrast hard left for 'normal'. All other checkboxes in there should be off, except shake mouse.

There is a key command for it, though I would expect that by default this would be inactive…
System Prefs &gt; Keyboard &gt; Shortcuts &gt; Accessibility