JTL A good oscilloscope can do that.
I know it can, but camera would show what really happens, especially how dithering is made on individual pixels level, whether it happens on all the brightness levels, etc.
cont-temp One thing that I am curious about is that if different color profiles on the macbook change the flickering at all. For example that deep-red with not the default screen color profile (color LCD) but for example with Adobe RGB (1998). And maybe with truetone/nightshift on and off if you have one of the newer versions of OS.
I checked various color profiles on MacOS yesterday (around 8 of them including Color LCD, Adobe RGB, Universal RGB, sRGB, Display P3). Each of them flickers on static deep-green color (rgb(0,50,0)) - some are better, some are worse, but differences probably come from the actual representation of this color on different profiles - it ranges from standard green (for brighter profiles) to almost black (for darker ones). Turning off font-aliasing didn't stop the flicker. Running Night Shift didn't change it too, although results were a little bit different than I expected - there was no added red subpixel component visible this time, maybe it's too subtle for camera, but I'll have to recheck it.
I also made a test with shades of gray getting down from 255 (white) to 0 (black) which shows obvious flickering at lower levels.
Another test I tried is checking how lagom's pixel inversion examples (http://www.lagom.nl/lcd-test/inversion.php) look under the microscope. There weren't any anomalies, they were shown as standard static pixels in different configuration.
I'll upload shades of gray and lagom's videos later, just for reference, although they don't seem to reveal too much.
Next step is checking browsers - Firefox Quantum vs. Safari vs. Chrome on MacOS - maybe some differences in font rendering will be easy to be spotted if one of them is using non-standard shading on the edges.
Here are 2 videos with grayscale and Lagom.nl tests: