Just tested on M1 Pro, 15.0 (Settings version) on Sonoma.

After initial custom color selection by clicking on the "+" (which works fine) and then reopening the Window to click "Custom Color" and then selecting the color again... it doesn't just jump for 20ms - it goes into full on psychotic flash jump behavior and basically continues to do so hands-off for 5 entire seconds before it stops at a random color.

There is 2 options now:

1) nobody has ever tested this workflow at Apple, automated or not.

2) it was tested and discovered but then pushed into the backlog as non-priority. Here the question arises - for how long?

The bug probably generates zero lost dollars so nobody at Apple cares anymore. THIS is what used to be different.