Another one for the road.
It's just a dark opaque 7 style skin.7
Even though I never figured out a transparent search box,
what bugs me more is the search box flashes for a brief instant.
What I now see happens, is part of the inside of dark-colored search box will show the desktop behind the menu,
( like when using a 24-bit selector bitmap instead of 32-bit on a transparent menu).
Problem is, it's an opaque menu with alpha opacity.
I can duplicate effect almost every time by hovering over submenu entries, then click on the search box.
If I switch to region opacity the flashing goes away, but due to the round menu corners,
extra artifacts there don't look so hot, so it has to be alpha opacity on this menu.
I might bring it up on GitHub, but I see there are only about 4 persons over there who help out when they have time,
and it's not exactly crippling menu operation.
Edit: Added opaque glass color for Windows 10. Now revision H
It does look a bit goofy.
Win7,8 will desaturate/wash out the color. Boost it in Color & Appearance settings,
or can improve slightly by adjusting CSM settings in "Menu Look" tab with:
Menu glass intensity: 50
Menu color blending:0