Hello,
I think, I've got the Solution, but for the problem itself, still I'm clueless ..

Dim Rn as Range


.TextFrame.TextRange.Text = "Author : " & H_Author
Set Rn = .TextFrame.TextRange
Rn.Font.Color = 9786419

This works fine, but I don't know why ...

Thank you for reading my problem !!!

Greetings from Berlin
Andreas