Widgets sidebar colors

Hi!

I want to define two diferent colors to the sidebar widgets. In css is the "h3" variable that defines the color and other things, and now I want to create one "h4" with other color!

I don't know how.... I think I've allready create an formating for "h4" but how can I define specifically the sidebar that i want to change?

Thanks (and sorry my gramatical erros!)