I want my Launcher to be transparent, so I check "Transparency" in Unity tweak tool and... it's solid. When I uncheck the transparency button... it is transparency. I've made gif to show it clearly.
How to make the launcher fully transparent?
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Maybe a bug. Maybe it’s because CCSM (CompizConfig Settings Manager) uses Opacity instead, so when you set Transparency OFF, probably it sets the Opacity equal to 0; thus it’s transparent. So if you want to make it totally transparent, you should move the slider position once and then put it on the tranparency 100% and also choose black for custom color, otherwise, it won’t be fully transparent. Here’s some screenshots:
Transparency 100% with a wallpaper-based color: it’s not transparent!
Transparency 100% with white: it’s not transparent but rather shiny!
Transparency 100% with black: it’s really transparent, but COF icon has a black background.
Transparency OFF with black: the same result as transparency 100%. Turning the transparency off means 100% tranparency (Opacity OFF)!
When setting transparency on, you have to adjust the transparency level with the slider just below the switch (on your screen capture it's at 100% so... plain solid indeed!)
Then, the fact that the launcher is still transparent when transparency is unchecked might be a bug. If you open CompizConfig (module 'Ubuntu Unity Plugin', tab 'Launcher') and the Unity Tweak Tool at the same time, you can see that the opacity is updated to 0 (ie. invisible) in CompizConfig when you uncheck the transparency option in Unity Tweak Tool.