Have a look at the Java documentation; Java iText version is very different from the current iTextSharp version but the API is well documented in some places so might give you ideas (it's helped me). You can find it on http://itextdocs.lowagie.com/docs/.
Are you trying to set the form fields font color using stamper? When I needed to have some dynamic text in color, I used the PdfContentByte object to create the text and then position it on the document, but not sure how would that work on the form with the stamper. Let us know.