Theme Brood; Change background color in widget area

Hey,

I’m totally new to wp (and this forum), but understood the basics of creating a child-theme for making changes in CSS etc. For days I’ve been trying to figure out how to change the background color of my widget-area in the sidebar of my theme to make it transparent in stead of an awful white color against my green background.

I tried adding the following code to my style.css, but it didn’t change a thing.

}
/* sidebar */
.widget {
background-color: rgba(255, 255, 255, 0.8);
padding: 25px;
margin-bottom: 30px;
}

Can anybody help me out?

Page is at http://www.caszavas.si.