Wpf: set textcolor to red doesn't work! Not Refresh the sheet

In Wpf:
```csharp
sheet.SetRangeStyles("B2:B2", new WorksheetRangeStyle()
{
  Flag = PlainStyleFlag.TextColor,
  TextColor = Color.Red,
});
```
dosen't work.Not Refresh the sheet. 
(If I save the sheet, and then, Load the sheet rfg file, the Color is red!)

But, In Winform:It works well.
A bug? 