Using the latest Start11 (1.22) and the latest insider build of Win 11 (22616.1) causes the taskbar to be invisible (no color). This is different to the system tray disappearing (that was a Win11 bug that's actually fixed in this build).
This seems to happen when I have the 'Use automatic color for the taskbar' option turned on.
If I turn off the automatic color option for the task bar, then the selected color displays, so there's a workaround.
I've un/re-installed start11 and rebooted and the problem persists.
I know this is an insider build of windows and isn't really supported, but just giving a heads up.
Automatic color on:

Automatic color off:

Thanks,
JimG.