Change background/text on 'Invite Friend' popup

On the 'Invite Friend' popup I have it that the text is dark and the background is dark, how can i change either of these please?

Hi

Please give me the link to the page. I will have a look and guide you what css file need to be modified (usually, it is a css file in your site template) .

Or if you know css, I suggest you to use Firebug plugin for Firefox. It is very easy to use this plugin to find and edit necessary css for a page !

Regards,

Tuan

The page is here: vmug.org.uk/index.php/component/eventboo...&event_id=1&Itemid=0

I really appreciate your help

Sorry to bump but can anyone help?