Please see attached workbook column_test.xlsx
Thanks for your posting and using Aspose.Cells for .NET.
We were able to observe this issue. Transparency becomes deeper on opening and saving the file. We have logged this issue in our database. We will look int it and resolve this issue. Once, the issue is resolved or we have some other update for you, we will let you know asap.
This issue has been logged as CELLSNET-41834.
Thanks for using Aspose.Cells for .NET.
Please download and try this fix: Aspose.Cells for .NET v184.108.40.206 and let us know your feedback.