Is there a way to turn off the boxes around the icons in Unity?
Clarification: I do not mean the backlight color -- there are plenty of questions about turning that off. I want the icons, and just the icons, to appear in the Unity bar, without any lights and shadows and borders. Can this be done?
The launcher icon overlays such as borders and highlights can be removed quite easily by changing 4 icon overlays in Unity.
Make a backup of the following image files in the folder
/usr/share/unity/4/:
launcher_icon_back_54.png
launcher_icon_edge_54.png
launcher_icon_glow_62.png
launcher_icon_shine_54.png
Either make your own transparent images of the same size or download the files at
wget -O transparent54.png "https://i.stack.imgur.com/MiFpK.png"
wget -O transparent62.png "https://i.stack.imgur.com/0NvP0.png"
Replace those 4 files with the same 4 files downloaded from the above link.
Restart unity by pressing Alt+F2 and typing setsid unity (or logging out and in again).
If you don't like it then just replace the icons with the backed up icons and restart unity.
Example:
