Scroll To Top plugin does the job with just one click a button appears when a person scrolls to the middle of the page to be clicked on.
Scroll to top plugin makes the scrolling of a page easier. It appends an icon at bottom of the page which attracts user attention. When the user click on this button it smoothly scrolls to the top of Webpage. Wp Scroll To Top plugin gives you custom settings which no other plugin gives.
You can set the position of icon.
It is user friendly and very easy to install.
Q.How to change the background color ?
Ans: All the options are available in free version now.