Modify source file after copy

I want to copy a file to a new location on an external drive that may not be there, only if that is successful then change the colour label of the source file. In other words, I want to use colour label to signify whether a step has been completed.
If I put "set colour label to …" after the copy command the file at the destination is changed, not the source.
How can I make the change to the source file?
If I put "set colour label to …" after the copy command the file at the destination is changed, not the source.
How can I make the change to the source file?