Changing background color style

I am trying to set the background color
I've tried this to set the background color but it is not working:
.aw-grid-header {
font-weight: bold;
color: blue;
background: red;
}

The text is blue and bold, but the background is not red.

Also, is it possible to set a style that is a pattern, fades from dark to light from top to bottom?

Thanks,
Raj