I'm having trouble with setting the color of a Brep in my C# component. The command FromArgb() takes four arguments which represents alpha, red, green, and blue. As I understand the first argument alpha, which can vary between 1 and 255, corresponds to the opacity of the previewed Brep (255 being solid and 1 being transparant). With my code below I manage to change the color but not the opacity. Changing int a below doesn't give any effect. The previewed Brep is always displayed as solid (255) no matter of the value of int a. Changing int r, g and b however gives effect on the previewed color. It is like the first argument doesn't have any effect.

Any Ideas??

int a = 180; // Opacity??
int r = 10; // red
int g = 10; // green
int b = 10; // blue

brep = nb;
alpha = a;
red = r;
green = g;
blue = b;

}

// <Custom additional code>
Brep brep;
int alpha;
int red;
int green;
int blue;

public override void DrawViewportMeshes(IGH_PreviewArgs args)
{
args.Display.DrawBrepShaded(brep, new Rhino.Display.DisplayMaterial(System.Drawing.Color.FromArgb(alpha, red, green, blue)));
}
// </Custom additional code>
}