I recently learned about the tagging system on macOS and tagged the file with name
DA1 with a yellow tag. Shortly after that, I removed the yellow tag but the file keeps popping up in my Finder window. What should I do to remove that file from Finder?
I have not found a stable way in the finder to apply tags. Usually any new method I try works for the first 5 files, and then the problems arise. Even the Get Info window will not reliably work (the tags appear to be fixed, but if you close the Get Info window and open it again, none of the changes have been kept).
However, recently I have been applying tags through an application's Save dialog box. Often this works to add or remove tags when the Finder doesn't. Maybe that will work for this problem file.
If I'm understanding you correctly, you tagged a file with the "yellow" tag, then later removed the tag. But when you view all files with that tag, that file appears in the view.
I would try restarting the Mac. That may flush the system. I have found adding or removing tags in the Finder to be completely unreliable. The problem has existed for years and in Sierra it's still not fixed. It may be that you thought you deleted the tag on the file, but it isn't actually removed.