Alpha not working for certain colors in Firefox 50

[hpinkos]

Reported on the forum: https://groups.google.com/forum/?hl=en#!topic/cesium-dev/lmPHhYxMd7c

In the example below, the wall should be transparent gray but shows up solid in Firefox. Red.withAlpha(0.5) works fine.

var viewer = new Cesium.Viewer('cesiumContainer');
var entities = viewer.entities;

var cartesianPositions = Cesium.Cartesian3.fromDegreesArrayHeights( [-71.4178416666667, 43.5730416666667, 50000, -72.3041944444444, 43.6261111111111, 50000] );

entities.add( {
    wall: {
        positions: cartesianPositions,
        material: new Cesium.Color.GRAY.withAlpha(0.5)
    }
});

viewer.zoomTo(viewer.entities);

The GREEN.withAlpha(0.5) in this example is also not working: http://cesiumjs.org/Cesium/Apps/Sandcastle/index.html?src=Rectangle.html&label=Geometries

[hpinkos]

@pjcozzi should this be labeled next release? I'm not sure if it's a bug with Cesium or a Firefox bug, but I feel like we should look into it soon.

[lilleyse]

Also here: #4658

[hpinkos]

@lilleyse Thanks, I missed that issue. Should we close this as a duplicate or is it a different issue?

[lilleyse]

It's the same issue, either one can be closed.