Simple Dialog box not displaying the actual color of the element inside it

Hello guys ,
i am calling a page using simple dialog box after clicking on a hyperlink.The page color was yellow so in dialog box obviously it was coming yellow.For a better look of dialog box i changed the color of that page to white using css injector.After that page color reflected as white.But calling it through simple dialog box it is coming in yellow(old color).... any idea?
Thanks
in advance