pdfView1.PdfBackColor = Color.Black;
var page = pdfView1.Document.Pages[pdfView1.CurrentPage];
foreach( var obj in page.PageObjects)
{
    if (obj is PdfPathObject)
    {
        obj.StrokeColor = Color.Green;
        obj.FillColor = Color.Black;
    }
    else
        obj.FillColor = Color.Green;
}