It's a bummer day for Classic Shell. I just upgraded to Windows 10 1903,
the version that has the Windows light mode menu theme (Light grey menu with boosted background color and added noise, and larger blur radius).
I was not expecting that new feature to work with CSM.
A big problem with CSM though.
Looks like any menu skin that uses glass color is now just shades of dark grey (devoid of color).
Only the Metro skin works because it has the designated Metro colors assigned in the skin file.
If and when you upgrade to Windows 10 1903,
it would be a good idea to head on over to Open-Shell and install their updated version to get glass color back.
I have not checked if every taskbar, start button, menu functions work correctly, but I am happy to have glass color working again.
EDIT:
Just an update.
Since I upgraded to 1903, there have been a number of Windows 10 cumulative updates installed on my computer.
One has fixed the no glass color issue.
I'm at KB4502584
I have switched back to using Classic Shell as glass
color working again.
Thanks, Microsoft and CS