I am writing a program that is supposed to make an Excel spreadsheet with some cells that are filled orange, given text, and given a border using a PropertyTemplate
Well, looks like it's a bug with Apache POI. I noticed someone posted about it in their bug tracker a while ago and it still exists in version 3.16.
In case anyone else comes across this issue, my workaround was to put the PropertyTemplate (the borders) on before filling any cells with my custom orange. It meant significantly modifying my code, but it works now.