color.darken(amount)

Add black and return a darkened color.
译：给颜色添加黑色并加深。

Arguments

amount — A number, from 0 to 100. Set to 10 by default.
译：：数字，0到100，默认为10。

# Create a new color, darken it 
blue = new Color("#28affa").darken(20)

layerA = new Layer
    backgroundColor: blue