showing webview with transparent background

I am displaying some graph from a link in webview.

My requirement is : I want to show graph with changed background color.

One way is to change the color in html/php code.

The other way I thought is to take the web view within NSBox and fill NSBox with required color, but it is not working as I require. It is showing graph with white background color in web view and NSBox with filled color around it.

Is there any way by which I can make background of WebView transparent so that it shows the color of box in which it is contained as background color of graph?

Thanks,

[myWebView setOpaque:NO];

[myWebView setBackgroundColor:[UIColor clearColor]];