GuiControl profile.fillcolor

[scriptless]

So I was wondering how I would get a background in a GuiControl to fill a certain color. Right now what I am trying does not seem to work.

PHP Code:

//#CLIENTSIDE
function onCreated() {
  preview();
}

function preview() {
  ("Window_test").Destroy();
  new GuiControl("Window_test") {
    useownprofile = true;
    profile.border = 1;
    profile.fillcolor = "50, 50, 50, 150";
    x = screenwidth / 2 - 162.5;
    y = screenheight / 2 - 150;
    width = 325;
    height = 100;
  }
}