How to style alongside default theme

How to style alongside default theme

Hi guys

I'm trying to theme my basic app - I'm looking to customise a few aspects mainly through additional DIV's using ID's and Classes, but I also want to change a few other bits.

For example I cannot get the background color to change. See below for my CSS:
.ui-page { 
    font-family: 'Museo', verdana, serif;
    background-color: #2b2e31;
}
 The font has changed but the background color isn't flowing through. Any suggestions?

Thanks