changing 'unread mail' colour

I'm trying to set up Mail to display all new unread emails in a colour (as possible in Entourage). As a default all you get is a small blue dot that is not so obvious.
Can I colour the whole line in a colour of my choice? (I want to apply this to all new or unread e-mails, not just some from my address book).

17'' powerbook 1Ghz & G3 iMac 700 Mac OS X (10.4.3)