A collection of commands that change the Arc Browser icon on macOS.
| Theme | Command | 
|---|---|
| Candy Arc | defaults write company.thebrowser.Browser currentAppIconName candy | 
| Hologram | defaults write company.thebrowser.Browser currentAppIconName hologram | 
| Neon | defaults write company.thebrowser.Browser currentAppIconName neon | 
| Fluted Glass | defaults write company.thebrowser.Browser currentAppIconName flutedGlass | 
| Schoolbook | defaults write company.thebrowser.Browser currentAppIconName schoolbook | 
| Colorful | defaults write company.thebrowser.Browser currentAppIconName colorful | 
- Copy one of the above commands
 - Open 
Terminal.app - Paste and run the command
 - Open Settings, then click the Icon tab
 - Click the new icon's radio button (it will already be selected, but clicking it will trigger the actual icon change) 1
 - The icon should be updated!
 
See @pv-g's comment.
Footnotes
- 
Thanks to @kotx for the tip to update without restarting Arc! ↩
 

Tbh, Im pretty much fine with what Arc gives, just accessible) I absolutely love Glass one!