I've installed a customized template with two columns, however, I'd like to make it looks in white color, in other words, I want to remove the borders of the content and sidebar so that everything look in white color. I have included a snapshot to make it clear for you to help me
So by looking at an image we are supposed to know what the code looks like and give you coding changes for code we cannot see. We will do that as soon as you demonstrate that you can thread a needle while wearing boxing gloves and a blindfold; or you could assume we are normal human beings who would benefit by you posting a link.
You should try this, while you are browsing your site right click on that element and then choose inspect element. you can see the css and the property locate the div id or div class on the browser and change the border to 0 border:0 or just border:none;