I'm not sure when it changed, but it's totally driving me crazy!!! The "Highlight" Color of the Selected Note is of such a minute color variation from the rest of the listed Notes, that I have a hard time distinguishing which Note is actually selected. I have 6 external (older) Dell LCD Displays connected to my Mac Pro, and I have to move at just the right angle to tell which Note is Selected.
I have looked for a Setting to change the "Highlight" Color for a Selected Note, but cannot find one anywhere. I do see the Option to "Use Dark/Light Sidebar", but this is not what I am looking for.