dreammanor: since you can see that with RichTextBox1.LoadFile (App.Path & "\sample.rtf") you have the exact same problem, you can realize that it is an intrinsic limitation (or bug in the fist case when it changes the colors) of the RichTextBox.

I tried with some other Rich Edit implementations with no result.

Did you consider using an OLE Container instead of the RichTextBox?

PS: I can't help you much with the OLE Container because I never used it.