Canvas colour: Action code on a html5 canvas

Hi there. I am working on a simple page by page story book in AA. It is a html canvas. 

On each page, i can change the page colour (outside of canvas) with this code. 

.backgroundColor = "your color";

Prob a super simple question but what is the action code for just changing the white canvas colour to something else? (without the need to draw a rectangle to fill the canvas). ? Thanks. Craig.