Я не панимаю вам .....
цвет заднего фона? -
Look & Feel >
Manage Skin Sets & Templates > ваш скин > Manage Templates in IP.Board > css > ipb_styles.css >
html, body { /* Safari has trouble with bgcolor on body. Apply to html tag too. */
background-color: #d8dde8;
color: #5a5a5a;
}