layer.backgroundColor

Sets the background color for this layer. The color is expressed as a string in the CSS color format. Layers have a light blue background color by default.
译：设置该图层的背景颜色。颜色表示为CSS颜色格式字符串。层有一个默认的浅蓝色背景色。

layerA = new Layer

layerA.backgroundColor = "red"
layerA.backgroundColor = "#00ff00"
layerA.backgroundColor = "rgba(134, 12, 64, 0.3)"
layerA.backgroundColor = "transparent"

# Remove the background color 
layerA.backgroundColor = ""