New picture message

Hello,

Pardon my English who are low

I'd like to change the skin of a forum, all are almost complete I just worry, I put an image in color when a new message is posted and another in black and white when the message was read, I can not find the place where it is necessary to link the images: s

Address of my test site: http://kira.legtux.org//index.php

Sincerely,
Kira