How to assign a white box (custom label) to a photograph

[TomHackettPhotography]

I have a number of images in Lightroom Classic that have white boxes for color labels.  I would like to assign this label to another image, but I can't remember how I did it.  

[John R Ellis · Accepted solution]

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A white label box appears when the text in the Label field in the Metadata panel doesn't match any of the texts in the current color label set (Metadata > Color Label Set). For example:

[TomHackettPhotography]

Thanks, John.  I needed to be reminded that I could edit the Label field in the Metadata panel.