@LukeJSmith Yes, you can format date columns using JSON if they are empty.
Here's sample JSON expression to check if date column is empty or not:
=if(Number([$DueDate]) == 0, 'Blank Date', 'Not Blank')
You can find other ways to check if date & time column is blank/empty at: SharePoint JSON formatting: Check if date & time column is blank/empty
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