I can't seem to get the shading to work

[ericdrosas87]

Code:

CSS.set_unit("vmin");
CSS.set_perspective();
CSS.group({n:"g1",w:450,h:450})
CSS.pyramid({n:"ship", g: "g1", x: 100, y: 200, w: 200, h: 100, d: 100, b: "#89A4D3", b1: "#6684B8", b2: "#ACC6F3", rx: -20})
CSS.camera({z:300, ry: 0, rx: 40, rz: 150});

setTimeout(() => {
    CSS.move({n:"ship", rz: 1000});
}, 1000)

For some reason though, the b1/b2 property values are not being applied to the different sides of the pyramid. What exactly am I doing wrong?