Hi rhino000,
You can create a new BaseColor from WebColor as:
BaseColor myColor = WebColors.GetRGBColor("#A00000");
Or
public static string mColor = "#aa8cc5";
int aa = Integer.parseInt(mColor,16); // base 16
int colorArr = Color.rgb(Color.red(aa),Color.green(aa),Color.blue(aa));
cell1.setBackgroundColor(new BaseColor(colorArr));
Try this.