Most of the web browsers do not print background colours by default. You can change your browser options to force the background colours to be printed.
Internet Explorer:
Open the options dialog box with
the Tools >
Internet Options... menu. Click
on the Advanced tab. Ensure
that the "Print background colors and
images" checkbox is checked.
Netscape & Mozilla
Firefox:
Before printing your report, select
File > Page
Setup.... Click on "Print background
(colors & images)".
You can now print your reports.