This only affects editors, as far as I can see:
When logged in via light mode, the admin menu does not
show up in the admin-only pages. (This is because all
the admin pages -- like the
story queue, the submissions bin, etc -- are designed
with the menu shown in a thin green bar accross the top
of the page, and it looks like the font is the same
color as that bar.)
The exception is the front page, because here the menu
is shown in dark type on a light background.
The menu items are still *there* even on the admin
pages where they don't show up; you can still roll your
pointer over them and click. But they're hard
(impossible) to read except in the browser's status bar;)
see attached screenshot.