Preview Window border color

I am using Audacity to add track numbers to multiple Wav files, I am using Windows 10 and Audacity V 3.4.2 Why when I open multiple files at the same time with the open command some of the preview windows are gray and some are brown

I don’t know what’s wrong but try Mp3Tag. (It works with WAV and all of the other popular formats.)

You can open a folder-full of files at once and then optionally edit all of the common information at once (like the artist & album title), or you can select one file at a time for the track number and other unique information. It also allows you to add album art, which Audacity doesn’t support. And, unlike Audacity, it only re-writes the metadata without re-writing the whole file. (That’s a big advantage with MP3s because it avoids another generation of lossy compression.)

Note that metadata is not as well-standardized or widely-supported on WAV. Almost all of the other formats are better for this.