ColorSvg

{
            Circle().SetFillColor(Rgb(1, 2, 3)).Render(cout);
            cout << endl;
        } {
            Circle().SetFillColor(Rgba(1, 2, 3, 0.5)).Render(cout);
            cout << endl;
        } {
            Circle().SetFillColor("black").Render(cout);
            cout << endl;
        } {
            Circle().SetFillColor("be").Render(cout);
            cout << endl;
        } {
            Circle().SetFillColor(NoneColor).Render(cout);
        }

<circle cx="0" cy="0" r="1" fill="rgb(1,2,3)"/>

<circle cx="0" cy="0" r="1" fill="rgba(1,2,3,0.5)"/>

<circle cx="0" cy="0" r="1" fill="black"/>

<circle cx="0" cy="0" r="1" fill="be"/>

<circle cx="0" cy="0" r="1" fill="none"/>