title: Background colour of line charts in chart.js
body: <p>I would like to change the background colour of the line graph produced by chart.js. There doesn't appear to be an option for this, and the documentation doesn't help. Extensive searching on the interweb has yielded no results. Is this possible?</p>
  
  <p>I must confess I don't really know much about the HTML5 canvas so I'm struggling a bit!</p>