Custom Page designing using CSS

Hi,
I am making product based website on my local computer wordpress using responsive theme. when i add new pages with page properties as below
Parent :No Parent
Template :Sidebar/Content

The page looks totally different from home page in terms of style .

How to customise the look of custom web pages using CSS.
1 ) I have added menu bar to the left of page and wants to customise using CSS.
2 ) How to change background colors of pages .

Please Help