Can't get plotBgColor() method working in tablesaw-jsplot

[Owen-Harris]

I am successfully plotting to a webpage using with the asJavascript() method with Javalin. However, I can't change the background color of the plot. Here's how I'm trying to do it:
Layout layout = Layout.builder("Average Temperature For Selected Period", "Year", "Average Temperature" ).plotBgColor("#BDE3FF").paperBgColor("#BDE3FF").build();