When clicking the whitespace between (say) the username and the "copy" text, the highlight color changes to give visual feedback that the field was copied. (Specifically, in light mode, it goes from a lighter shade of the system highlight color to a darker shade on mousedown.) When clicking the username itself, or the "copy" text itself, the highlight color does not change.
1Password Version: 7.3.BETA-3
Extension Version: Not Provided
OS Version: Not Provided
Sync Type: Not Provided