I want to change background color in the editor side like in the example picture.
How can I do?
Just go to
Options --> Configure TeXstudio --> Syntax highlighting and choose what you want to change and with which color.
I am not sure if I understood your question correctly, but if you are wondering were the green-background lines in your picture are coming from, they are due to comments in capital letters (and a few others).
Try a line with
% TODO buy more rubber ducks :)
see http://texstudio.sourceforge.net/manual/current/usermanual_en.html#SECTION14
Option --> Configure TeXstudio --> Syntax highlighting(I don't know if this is the exact naming because I have the Italian version) and then choose what you want to change and with which color. For more advanced setting see here or here. – CarLaTeX Oct 31 '16 at 08:26