Created Unassigned: Changing named style only by open+save [15427]

After days of trying to solve this mistery, I finally gave up, and asking for your help:

So I have got this excel with a style named "Normal" and it has a Built-in Id 0 (don't know if it matters at all).
Originally it has no special attributes, not any background nor any pattern color.

After using the code below ("pure" open and save) the named style is changed and has a blue background color, cause why not...

```
using (ExcelPackage excelPackage = new ExcelPackage(new MemoryStream(File.ReadAllBytes(EXCEL_PATH))))
{
using (ExcelWorksheet ws = excelPackage.Workbook.Worksheets[1])
using (ExcelWorksheet ws2 = excelPackage.Workbook.Worksheets[2])
{
using (Stream stream = new MemoryStream())
{
excelPackage.SaveAs(stream);
File.WriteAllBytes(EXCEL_PATH, stream.ReadToEnd());
}
}
}
```

It's obvoiusly a big issue for me, because anytime I try to manipulate any content in the file, I got some ranges with this new annoying blue background color.

Added infos:
- on client side I use DevExpress's XtraSpreadsheet (WinForms) component to save the excel file I try to manipulate with EPPlus later on the server side
- after applying _ANY_ change in the file with MS Excel and saving, the manipulation does not have that random effect